Scholars' Mine
Masters Theses Student Theses and Dissertations
1960
The dielectric strength of some anti-corrosive paints
John Harvey Gustafson
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THE DIELECTRIC STRENGTH OF SOME ANTI-CORROSIVE PAINTS
BY JOHN HARVEY GUSTAFSON
A
THESIS
· submitted to the faculty of the
SCHOOL OF 1ITNES AND Mb.-vrALLURGY OF THE UNIVERSITY OF MISSOURI
.in partial fulfillment of the work required for the
Degree of MASTER OF SCIENCE, CHEMISTRY MAJOR Rolla, Missouri
1960
\ A ( Approved by
\./\..)~~advisor)
~iu? ii
TABLE OF CONTENTS
Page LIST OF FIGURES . . v
LIST OF TABLES. . • . • • • • • . viii
I. INTRODUCTION . • • . • . • • • • • 1
II. LITERATURE REVIEW. . • 3
Dielectric Strength and Dielectric Constant. 3
Theory of Dielectric Strength. • • • . . • • • 3
Factors Influencing Dielectric Breakdown • • • 4
External Heating • • • • • • • 4
Internal Heating . • • . • . • • • . 5
Duration of Stress • • . . • • • • • • • • . 6
Specimen Thickness • . • • • • • . 6
Moderate Direct Current Str~ss . • • . • • . 7
Moisture • . • • • 7
III. EXPERIMENTAL • • . • • • • . • • 9
Purpose of Investigation. • • • • • • . • . 9
Plan of Investigation. • • • . . • • • • • • • . 10
Literature Review. • . . • • • • . • 10
Experimental . • . • • . • • • • • 10 Correlation of Data. 10
Materials. • . • • . • • • • • • • • . • • • • • • 11
Apparatus. • • • • • • . • . • • 18
Pnemnatic Thickness Gage . • . • • • . 18
Electrical Circuit . • • • • • • • • • 31 iii
Method of Procedure •••• ...... 33
Coating Steel.Panels ...... • • . . 33 Determination of the Thickness of Dry Paint Films with the Pneumatic Thickness.Gage •••••••••• 35
Determination of the Breakdown Voltage. • • • • 38 Data and Results •• ...... 43
Sample Calculations...... • • . . . • • 101 Calculation of the Dry Film Thickness. • . . . •• 101 Calculation of the Average Dry Film Thickness. . . . . 101 Conversion of Recorder Readings to Breakdown Voltag°es • • • • • • • • • • • . . . • • 101 Calculation of Dielectric Strength. . . • • • • • 102
Rejection of a Dielectric Strength Value • • • •• 102 Calculation of the Correlation Coefficient. . . . .• • 103 Calculation of the Equation for the Regression Line. • • • • • • • • • • • • • • • • • • 106 Calculation of the Residual Variance about the Regression Line ••••• ...... • 106 IV. DISCUSSION • ...... • 108
Discussion of Results •• • • ...... • 108
Recommendations. • . . • • • ...... • 111
Limitations. • ...... • • ...... • 113
v. CONCLUSIONS. • . . • . . . . • . . • . . • 114
VI. SUMMARY. . • • . . • . . • . . . . . • . . • ...... 115
VII. APPENDICES . . • • . • . • . . • • . . • . • . • . . 117
Appendix 1 (Materials) . • • • . . • . 118
Appendix 2 (Apparatus) . . . . • . • . . . 119
Appendix 3 {Calibration of Pneumatic Thickness Gage) • . . 122 Appendix 4 {Correlation Coefficients). 126
Appendix 5 (t Valu~s). • . 127
VIII. BIBLIOGRAPHY...... • • . 128
IX. ACKNOWI,EDGMENTS. • • • • 131
x. VITA • • . 132 v
LIST OF FIGURES
Page
Figure 1. Pneumatic Thickness Gage with Rotameter Connected. • • • • . • • • • • • • 0 • • • • • • • 21 Figure 2. Isometric View of Pneumatic Thiclmess Gage. • • • • . 22
Figure 3. Pneumatic Thickness Gage. • • • • • • • • • • • • • • 23
Figure 4. Pneumatic 'fhickness Gage, Front View. • • • • • • • • 24
Figure s. Pneumatic Thickness Gage, Right Side View • • • • • • 25
Figure 6. Pneumatic Thickness Gage, Top View. • • . • . . • • • 26 Figure 7. Pnewnatic Thickness Gage, Isometric View of Gage Arm. • • • • • • • • • • • • • ... • • • • • • 27 Figure 8. Barrel Assembly Mounted in Gage Arm • • • • • • • • • 28 Figure 9. Working Portion of Pneumatic Thickness Gage Disassembled. • • • • • • • • • • • • . • • • • • • 29 Figure 10. Pneumatic Thickness Gage, Details C and D. • • • • • 30 Figure ll. Wiring Diagram for Electrical Circuit • . • • • • • • 32 ltigure 12. Baker Film Applicator Blade and Gardner Automatic Film Applicator. • • • • • • • • • • • • 34 Figure 13. Steel Panel with Masonite Template Clamped in Position. • • • • • • • • • • • • • • • • • • • 40 Figure 14. Section of Recorder Chart • • • • • • • • • • • • • • 41
Figure 15. Masonite Template and Ball Bearing Contact. • • • • • 42 Figure 16. Breakdown Voltage Versus.Average Film Thickness: Vinyl Primer. • • • • • • • • • • • • . • • • • • • 51 Figure 17. Breakdown Voltage Versus Average Film Thickness: Chlorinated Rubber Primer. • • • • • • • 0 • • • • 52 Figure 18. Breakdown Voltage Versus Average Film Thickness: h))oxy Ester Primer. 0 • • • • • • • • • • • • • • • 53 Figure 19. Breakdown Voltage Versus Average Film Thickness: Alkyd Primer. • • • • • • • • • • • • • • • • • • • 54 .,.. .. .
vi
Figure 20. Breakdown Voltage Versus Average Film Thickness: Oil Primer. • • • • • • • • • • • • • • • • • • • • SS Figure 2lo Breakdown Voltage Versus Average Film Thickness: Phenolic Primer. • • • • • • • ... • • • • • • • • • 56 Figure 22. Comparison of Breakdown Vo~tage Versus Average Film Thickness for the Various Primers • • • 57 Figure 23. Breakdown Voltage Versus Average Film Thickness: Vinyl Finish. • • • • • • • • • • • • • • • • • • • 66
Figure 24. Breakdown Voltage Versus Average Fil... 'll Thiclmess: Chlorinated Rubber Finish...... • • 67 Figure 25. Breakdown Voltage Versus Average Film Thiclmess: h'poxy Ester Finish • ...... • . . . . . 68 Figure 26. Breakdown Voltage Versus Average Film Thickness: Alkyd Finish. . . • ...... 69 Figure 27. Breakdown Voltage Versus Average Film Thickness: Oil Finish. • ...... • ...... 70 Figure 28. Breakdown Voltage Versus Average Film Thickness: Phenolic Finish...... 71 Figure 29. Comparison of Breakdown Voltage Versus Average Film Thickness for the Various Finishes. 72 lt.,igure 30. Breakdown Voltage Versus Average Film Thickness: Vehicle of Vinyl Primer. . . • ...... 80 Figure 31. Breakdown Voltage Versus Average Film Thickness: Vehicle of Chlorinated Rubber Primer. . . . . 81 Figure 32. Breakdown Voltage Versus Average Film Thickness: Vehicle of Epoxy Ester Primer...... • . . . • 82 Figure 33. Breakdown Voltage Versus Average Film Thickness: Vehicle of ilkyd Primer...... • • • . • . . • • 83 Figure 34. Breakdown Voltage Versus Average Film Thickness: Vehicle of Oil Primer...... • . . • . . • • 84 Figure 35. Breakdown Voltage Versus Average Film Thickness: Vehicle of Phenolic Primer. • ...... • . . . • 85 Figure 36. Comparison of Breakdown Voltage Versus Average Film Thickness for the Various Primer Vehicles...... • . . . . • . 86 vii
Figure 37. Breakdown Voltage Versus Average Film Thickness: Vehicle of Viny1 Finish...... 94 Figure 38. Breakdown Voltage Versus Average Film Thickness: Vehicle of Chlorinated Rubber Finish. . . . . • • . 95 Figure 39. Breakdown Voltage Versus Average Film Thickness: Vehicle of Epoxy Ester Finish...... • . . 96 Figure 40. Breakdown Voltage Versus Average Film Thickness: Vehicle of Alkyd Finish•••••••••••• 97 Figure 41. Breakdown Voltage Versus Average Film Thickness: Vehicle of Oil Finish••••••••••••• 98 Figure 42. Breakdown Voltage Versus Average Film Thiclmess: Vehicle of Phenolic Finish •••••••••• 99 Figure 43. Comparison of Breakdown Voltage Versus Average Film Thickness for the Various Finish Vehicles. • • • • • • • • • • ·• • • 100 Figure 44. Calibration Curve for Pneumatic Thiclmess Gage •• 124 Figure 45. New Scale Installed in Rotameter •••••••• . . . 125 viii
LIST OF TABLES
Page
TABLE I. Composition of Primers. . .. . • . • . . . • . 13 TABLE I. Composition of Primers ( continued) • . . • 14
TABLE II. Composition of Finishes . . . . • • . . • 15
TABLE II. Composition of Finishes (continued) . • • • • . • . 16
TABLE III. Phenolic Varnish...... • . . . • • . . . 17
TABLE IV. Dielectric Strength of Vinyl Primer. • . 44
TABLE v. Diele_ctric Strength of Chlorinated Rubber Primer. • 45
TABLE VI. Dielectric Strength of Epoxy Ester ~rimer . • . • . 46
TABLE VII. Dielectric Strength of Alkyd Primer. . . • . . . . 47
TABLE VIII. Dielectric Strength of Oil Primer. . . . • . 48
TABLE IX. Dielectric Strength of Phenolic Primer. . • . 49
TABLE x. Comparison of Results of Primers. . . • . . • • 50
TABLE XI. Dielectric Strength of Vinyl Finish. . . • . . . • 58 TABLE XI. Dielectric Strength of Vinyl Finish (continued) . . 59 TABLE XII. Dielectric Strength of Chlorinated Rubber Finish. . 60
TABLE XIII. Dielectric Strength of Epoxy Ester Finish • • . 61
TABLE XIV. Dielectric Strength of Alkyd Finish. . . • . 62
TABLE xv. Dielectric Strength of Oil Finish...... • 63
TABLE XVI. Dielectric Strength of Phenolic Finish. . • . • . • 64
TABLE XVII. Comparison of Results of Finishes. . . . . • • 65 TABLE XVIII. Dielectric Strength of Vehicle of Vinyl Primer. 73 TABLE XIX. Dielectric Strength of Vehicle of Chlorinated Rubber Primer. • • ...... 74 TABLE xx. Dielectric Strength of Vehicle of Epoxy Ester Primer. . . • • ...... 75 TABLE XXI. Dielectric Strength of Vehicle of Alkyd Primer . . 76 TABLE XX.II. Dielectric Strength of Vehicle of Oil Primer. . . 77 TABLE XX.III. Dielectric Strength of Vehicle·of Phenolic Primer. 78 TABLE XXIV. Comparison of Results .of Primer Vehicles • • • 79 TABLE XXV. Dielectric Strength of Vehicle of Vinyl Finish •• 87 TABLE XXVI. Dielectric Strength of Vehicle of Chlorinated Rubber Finish •• ...... 88 ·TABLE XXVII. Dielectric Strength of Vehicle of Epoxy Ester Finish ••••• 89 TABLE XXVIII. Dielectric Strength of Vehicle of Alkyd Finish • • 90 TABLE xxn. Dielectric Strength of Vehicle of Oil Finish. . . 91 TABLE XXX. Dielectric Strength of Vehicle of Phenolic Finish. 92 TABLE XXXI. Comparison of Results of Finish Vehicles • . . . . 93 TABLE X.XXII. Values Required for Calculation of the Correlation Coefficient of Vinyl Primer ••••• 104 I. INTRODUCTION
Metals undergo chemical reaction with nonmetallic elements of their
surroundings to produce compounds which are either oxides or salts. These
corrosion products, as they are called; may accelerate, :impede, or have
no influence on the course of further corrosio~. It is unfortunate that
iron, the metal of greatest use to man, recieves very little protection from its corrosion products. There are no easy or inexpensive means of
prevention of this corrosion and at best the reactions can only be controlled. One method of control is the use of anti-corrosive paints.
Their protection is produced by placing an inert, continuous, and adhering
film between the metal and its surroundings. It is a well known fact
that some of these paints protect the metal much better than others. The
evaluation of the degree of protection by field tests is time consuming
and it is desirous to find a laboratory method which will el:uninate the
t:une factor and give reliable results.
At present, field tests are the most :important for the consumer
for it is with these that he can see how a particular coating will per
form under his conditions. A few laboratory or preliminary tests have
been designed for the purpose of eliminating some products before they
reach the field test stages. Some of these are: exposure to accelerated weathering or salt spray, detennination. of water-, ion-, and oxygen-per meabilities, testing for elongation-tensile strength, and the use of the
Protectometer (an electrical device to measure the resistance of the paint films). For the most part the correlation of these tests with field re
sults have been inconclusive. Since corrosion is mainly an electrochem- 2
ical process it would be interesting to investigate these coatings on their electrical insulating properties, for instance the dielectric strengtho
A coating w.i. th a high dielectric strength would be expected to have great insulating power against electrical flow. If in addition, there would exist a correlation between the dielectric strength and the anti-corrosive properties of a coating, the detennination of the dielectric strength would make an easy and quick method of evaluationo The purpose of this investigation was to determine if: 1. there is a significant difference in the dielectric strength of some connnercial types of anti-corrosive paintso
2o the dielectric .strength is independent of the film thicknesso 3o there is a relationship between the anti-corrosive protection and the dielectric strength. 3
II. LITERATURE REVIEW
The literature reviet-r includes the basic theories of dielectric strength and the factors influencing dielectric· breakdom10
Dielectric Strength and Dielectric Constant
Dielectric strength must not be confused tri. th dielectric constant since they are essentially unrelatedo "The dielectric constant deter- mines how much charge a given condenser ,till store up ,dth a given poten- tial difference; dielectric strength determines how much voltage the condenser l'1ill stand without being broken dolffl."( 24) o
Theocy: of Dielectric Strength
When an electric field exists ,tlthin a dielectric material, the electrons become slightly displaced relative to their nuclei, but still remain boW1d to the nucleio This situation is maintained so long as the electric intensity is sufficiently lo,-r. There is a certain value of this intensity lihich is sufficient to pull the electrons amLy from the atoms to which they belongo When this separation occurs in a gaseous or a liq id material., it becomes ionizedo When this happens in a solid dielectric, the material becomes ruptured, broken, or punctured by ·a discharge through ito The point at lmich this breakdo1·m will take place is called the elec tric or dielectric strength. Its wri.ts are generally expressed as kilo- volts per centimetero
Early theories approached the phenomanon of dielectric breakdot-m by way of analogy lfith mechanical failure of metals or that the breakdo'Wn. 4
began from microscopic cracks or scratches(Jl). Somewhat related to these
ideas were those which related breakdown to mechanical stress which arises from the electrical field. This was shown to be true for mechanically
weak or soft dielectrics where localiz~ stresses were caused by pointed 2 electrodes or very heavy electrodes supported by a small area( ). 2 von Hippel( S) was the first to consider the behavior of electrons in the solid dielectrics. He assembled evidence that breakdown was electronic in character and took the form of an avalanche arising from a self increas- ing stream of electrons. His criterion that free electrons should mult- iply was that they should gain more energy from the electric field than they lost in stimulating oscillations of the solid structureo They \rould continue to be accelerated until they freed more electrons by ionization. 4 A theory which is very closely related to von Hippel 's is that of Frolich(l ). His theory does not assume that the electrons always move in the field direction and are gradually accelerated. He takes account of the scat- tering and considers the rate of change of electronic energy on the aver- age over many_ collisions. Some of the consequences of his theory are discussed in the following sections.
Factors Influencing Dielectric Breakdown
External Heating. The dielectric strength of a solid is lowered . (1218 19,20,21,27,32) . (14) by external heating ' ' ' • Frohlich's theory states that below a certain temperature the electric strength should either in- crease with or be independent of temperature, while above this critical point the electric strength should ·decrease w.i th increasing temperature according to the relation: Fo · Where: F is the electric strength Tis the absolute temperature Oakes(l9) states: The critical temperature predicted by the ·electronic theory is that temperature at which the density of electrons in the conduction levels becomes sufficiently great for energy transfer betl'leen electrons to influence the initiation of breakdolm; below this temperature the density of electrons is so small that they can be considered independ- ent of each othero · von Hippel and Alger<29) give results on ionic crystals which sho,·1 a breakdot-,n voltage rise with temperature to ·a critical point and then the breakdo,m voltage falls off 1-Tith further increase in temperatureo von Hippel and Lee(JO) suggest that the falling electric strength with increasing temperature characteristic of solid amorphous dielectrics is the result of an increasing number of electrons being generated ow.i.ng to the decreased recombination with positive ions at higher temperatureso They also in- dicate that the materials which have a falling electric strength m.th in- creasing temperature characteristic have probably a colloidal structure so that electronic or ionic motion may take place along internal surfaceso The phenomenon of absorption, adsorption, and permeability ttith respect to polar substances eogo water vapor, may be cited as evidence that such surfaces exist in organic films and exhibit attractive forceso Studies done by Ball(J) on polyvinyl alcohol imply that the pres~ce of dipoles is the determining feature in the:faUing electric strength m.th increasing temperature cha.racteristico Internal Heatingo Whitehead(JJ) states, "electrons moving in the ' electric field lose energy in the form of heat to the solid structure". Energy loss from direct current could be accounted for by r2R heating.and would be expected to be less than alternating current tmich muld exhibit r 2R heating and also loss of energy in the form of heat in the relaxation cycle l-rltlch could arise f~m dipolar motions o Since the loss of energy would increase l·ti.th field strength, it could become high enough that the solid would not be able to dissipate tl:te heat generatedo The temperature of that area would rise and breakdown ensue earlier than expected since 23 the electric strength falls with increasing temperatureo Schwaiger< ) reports that the electric strength of mica is 20 per cent higher l·r.ith 9 direct current than itlth alternating currento Oakes (l ) reports polythene to have the same tendency o Duration of Stresso Sch~.raiger(ZZ) reports that work done indicated that due to the internal heating effect, the shorter the duration of stress the higher the voltage that may be applied to breakdotmo Thomas and Griffith(27) made tests to determine the effects of :maintained volt- age on the electric strengtho A sphere to plane electrode system t1as usedo For the examination, maintained voltages were compared to results obtained for a rise to breakdown in from 30 to 60 seconds o In the case of the maintained voltage tests, the puncture was in nearly every case an appreciable distance from the point of contact of the spherical elec trodeo The explanation given for this was that the area arotmd the point of contact, in time, becomes charged to the same potential as the sphere and that the breakdom1 took place at the lreakest point in this areao With a fairly rapid rise of voltage, the surrotm.ding area 11ill lag behind the sphere's potential and the breakdol"m then occurred in a small area below the electrodeo Specimen Thiclmesso Frohlichts theory(l4) states that, "the electric strength should be independent of thickness until the latter 7 approaches the electronic mean free path, when the electric strength should increase with decreasing thickness". This was substantiated in the articles reviewed where the relationship of .breakdown voltage versus thickness was showno In very thick samples· there was a slight decrease in breakdown voltage with thickness. In all cases this was assumed by the authors to be due to the internal heating effecto Moderate Direct Current Stress. Garton and Church(lS) report that breakdown tmder moderate direct current stress is nonnally of an electrochemical nature. They suggest that leakage current is conveyed by ions originating from slight dissociation of the insulating material or from trace impurities such as moisture or organic acids and that they may attack the insulation. When chlorinated hydrocarbons fonn part of the dielectric, cathodic reduction leads to release of HCl, which can chemically attack the electrodes or other components of the dielectric(4,ls). Berberich and Friedman(4) and Egerton and McLean(lG) have shown that the rate of deterioration of capacitors having chlorinated hydrocarbons is decreased by the addition of small amounts of quinones, maleic aneydride, sulfur, aromatic azo compounds, and benzil. Stabilization was attributed to the fonnation of a protective film on the electrodes(lG) or a coordi- nation complex between the stabilizer and A.1.CJ.3 formed during the deteri oration (4). 34 Moisture. Whitehead( ) indicates that moisture has devestating effects on the dielectric strength of most organic insulators. The range of materials which are effectively impervious to moisture is restricted. Metals and some mineral dielectrics.possess this property, but most organic dielectrics are subject to molecular diffusion of moisture with varying 8 degrees. Values of moisture penneabilities collected or quoted by Thomas and Gent (26) range from ~O -6 to 10-9 g m/hr / cm2 for various connnercial insulating materials. No literature could be fol.llld showing the effect of moisture on the dielectric strengtl?-. 9 III. EXPERIMENTAL The experimental section of this thesis is divided into the fol lowing sections: (1) purpose of investiga:tion, (2) plan of investigation, (3) materials and equipment used, (4)' method of procedure, (5) data and results, and (6) sample ca.lculationso Purpose of Investigation The purpose of this investigation was to detennine: lo if there is a significant difference in the dielectric strength of some connnercial types of anti-corrosive paintso 2o if the dielectric strength is independent of the film thick- nesso 3o if there is a relationship between the anti-corrosive protect ion and the dielectric strengtho 10 Plan of Investigation The plan for this· investigation was divi~ed into three main sec tions: (1) literature review, (2) experimental, and (3) correlation of data. Literature Reviewo The literature reyiew of this investigation was conducted with two ideas in mind: (1) to review for the reader the theoretical essentials of dielectric breakdown and (2) to show the factors influencing this type of breakdowno Experimentalo Anti-corrosive coatings of various types were ob tained from commercial sourceso These coatings were laid down on polished steel panels and the thickness determined with a pneumatic thickness gage constructed for this investigationo The films were broken do1,m by direct current of high voltage and the dielectric strength calculated. Correlation of Datao Experimental data for primers, finishes, primer vehicles, and finish vehicles were evaluated by a method of statisticso 11 Materials With the exception of the paint fonnulations, all materials used are listed in Appendix 1. Paint Fonnulations. The paints that were used in this research were proprietary materials supplied for CorrQsion Project No. 1, under- taken at the North Dakota Agricultural College and continued at the School of Mines and Metallurgy for the Corrosion Comrni ttee of the Federation of Societies for Paint Technology. The following primers, finishes, and vehicles of same were used: Primers: Red Lead Alkyd Primer (Rinshed-Mason Reference Noo XR-8952, Federal Specification TT-P-86a, Type III)o Red Lead Epoxy Ester Primer (Shell Reference No. 456-19). Red Lead Vinyl Primer (Bakelite Reference No. XE-5259, Federal Specification 1ITL-P-15929). Red Lead Linseed Oil Primer (DuPont Reference Noo 2050, Federal Specification TT-P-86a, Type I). Red Lead Phenolic Type Primer (Devoe and Raynolds Reference No. ML-1893, Federal Specification TT-P-86a, Type IV). Red Lead Chlorinated Rubber Primer (Hercules Powder Reference Noo X-8916-89-3). Finishes: Gray Alkyd Type House Paint (Rinshed-Mason Reference No. XR-8988, Federal Specification 1ITL-P-15130-A). Gray Epo:xy Ester Finish Coat (Shell Reference No. 456-19). Gray Vinyl Type Finish Coat (Bakelite Reference No. XE-5403, Structural Steel Council Specification No. 9). Gray Linseed Oil Type finish Coat (DuPont Reference Noo 2050, Federal Specification TT-P-102, Amendment 2, Class B). 12 Gray Phenolic Type Finish Coat (Devoe and Raynolds Reference Noo ML-1892, Structural Steel CoW1cil Specification SSPC-105-SST) • Gray Chlorinated Rubber Finish Coat _(Hercules Powder Reference No. X-8916-88-3). Vehicles: The vehicles of each of the above were obtained either from the manufacturer, or prepared from the raw materials, or obtained by centrifuging the primer or finish until the clear vehicle could be decanted. The fonnulations of the primers and finishes are given in Tables I, II, and III. 13 TABLE I Composition of Primers (per cent by weight) Paint Type Oil Phenolic Chlorinated Rubber Red Lead Oxide 77.04% 55.90% 18.33% Indian Red 0.50 Zinc Chromate 3.36 Aratone 270 3.13 Ashes tine 4.43 Fibrene 7.74 Celite 281 5.32 Aluminum Stearate 0.29 0.24 0.27 _ Duraplex 22.33 Soya Lecithin (50%) 0.17 Varnish* 26.03 Parlon S-20 11.00 Raw Linseed Oil 11.32 Pale Heat Bodied Linseed Oil 3.54 Mineral Spirits · 7.47 7.81 6.67 Solvesso 100 26.67 Cobalt Naphthenate (6%) 0.08 Lead Naphthenate (24%) 0.11 o.i9 Manganese Naphthenate (6%) 0.06 100.0~& 100.00% 100.00% * Varnish (per cent bv weight) BR-4036 Bakelite Phenolic Resin 20.0% China Wood Oil 40.0 Mineral Spirits 40.0 100.0% 14 TABLE I (continued) C.Omposition of Primers (per cent by weight) Paint Type Alkyd Epoxy Ester Vinyl Red Lead Oxide 64.09% 56.30% 22.00% Dia tomaceous Silica 5.30 Aluminum Silicate 0.20 Aluminum Stearate 0.25 0.26 Tricresyl Phosphate _ 3.00 Alkyd Res:in (Beckosol P-671) 29.31 Bakelite Vinyl Resin VAGH 15.00 Epon Ester S-8 Resin 25.80 Methyl Isobutyl Ketone 30.00 Mineral Spirits 6.15 8.00 Toluene 30.00 Cobalt Naphthenate (6%) 0.10 0.10 Butyraldox:i.me 0.10 0.04 100.00% 100.00% 100.00% 15 TABLE II Composition of Finishes (per cent by weight) Paint Type Oil Phenolic Chlorinated Rubber Titanimn Dioxide 7.35% 10076% 32.00% Lamp Black 0.26 0.30 Ultramarine Blue 0.43 White Lead 20.40 Zinc Oxide 16.49 30.72 Magnesimn Silicate 19034 Dyphos 0.40 Bentone 34 0.63 Anti-Oxidant 0.09 Glyptal 2466 22.33 Parlon s-20 11.00 Phenolic Varnish* 55.86 Bodied Linseed Oil 5.83 Raw Linseed Oil 23.44 Mineral Spirits 6.79 7.67 Toluene 1.28 Solvesso 100 25.67 Cobalt Naphthenate (6%) 0.17 Lead Naphthenate (24%) 0.24 0.43 Manganese Naphthenate (6%) Ool2 100.00% 100.00% 100.00% -it- Phenolic Varnish - see Table III. 16 TABLE II {continued) Composition of Finishes (per cent by weight) Paint Type Alkyd Epoxy Ester Vinyl Titanium Dioxide s.15% 26.62% 12.00% Chrome Yellow 0.12 La.mp Black 0.10 0.24 Zinc Oxide 18072 3.00 · Magnesium Silicate 13.10 Alkyd Resin (Beckosol 296-70) 39.31 Bakelite Vinyl Resin VYHH 16.00 Epon Ester S-8 Resin 30.00 Tricresyl Phosphate 3.00- Hi Flash VM & p Naphtha 6008 Methyl Isobutyl Ketone 34.50 Mineral Spirits 16.85 40.00 Toluene 34050 Cobalt Naphthenate (6%) o.1s 0.02 Lead Naphthenate (24%) 0.39 Manganese Naphthenate (6%) 0.15 100.00% 100.00% 100.00% 17 TABLE III Phenolic Varnish (per cent by m~ight) Linseed Oil 17021% China Wood Oil 26008 Bakelite BR-254 16071 Mineral Spirits 30064 Toluene 3o72 Dipentene 4o48 Solvesso 100 lol6 100000% 18 Apparatus The list of equipment along with specifications, manufacturer or supplier, and use is found in Appendix 2o In the following section the Pneumatic Thickness Gage and the Electrical Circuit are describedo Pneumatic Thickness Gageo Various devices and methods have been developed for the measurement of the thickness of attached films of pro tective and decorative coatings as trell as films of plastic, paper, metals, etco An accurate measurement of the thickness of these materials both from research and economic standpoints is very importanto Most of these instruments used in the paint industry have been designed primarily for general use in the field and checking of the mrl. fonni.ty of productso Some of these instruments, while being very conven ient to handle, lack the accuracy ne.cessary for research l·rorko Others, i·1hile obtainjng the necessary accuracy, require the destruction or pen etration of the film, ,mich llllder most conditions is a disadvantageo Gages have recently been designed ,-J'hich operate by radiation penetration or scattering, but these are expensive and require calibration for each material usedo The Pnetunatic Thickness Gage has the advantage that it has great accuracy and does not destroy or penetrate the filmo The results obtained with this gage are independent of the composition and the thickness of the base ma.terialo The base may be of any solid material and need not be magnetico The gage is calibrated after construction and as long as it is used lrl.thin its calibration range, only occasional checks are necessaryo . 19 There are no delicate parts that can be damaged, and the thickness range is variable depending on.the equipment used. Disadvantages are its size and weight, time required for stabili- zation, and the requirement that the coating or film must not be easily compressed. Pneumatic thickness gages have been described by many authors(9,lo, 11 12 13 , , , 17) and all fall into two main catagories: those employing pressure differential and others depending on the flow rate of a gas. The differential pressure systems have the advantage that there are nu- merous methods, both mechanical and electrical, that can be used to in- crease the sensitivity and versatility. The second type is lilllited to instruments which measure flow rate of a gas, for example, a rotameter. The latter method was chosen for this investigation because of the avail- ability of equipment. The principle of operation is as follows: Compressed air that has been dried and cleaned in a filter is allowed to flow .from a small hole (0.070 inches) in the measuring head (nozzle) of the gage. The downstream pressure is controlled, and the flow from the measuring head is at a crit- ical velocity when not restricted. The head of the gage is located direct ly above and approximately 2 mil~ (0.002 inches) from the surface to be measured. As the perpendicular distance between the measuring head and the surface is decreased, frictional forces are set up which in turn are responsible for a decrease in flow rate indicated on a precision rotameter. This change in flow rate is directly proportional to the variance in per- pendicular distance between the head and the surface. By proper calibration the film thickness may be read directly from the rotameter scale or the 20 difference of readings obtained on the bare and the coated substrate. The scale of the rotameter is calibrated against known standards and if used within its range, no further calib~ation is necessary, con trary to other types which require standardization with change of mater ials, voltage, etc. Construction details of the pneumatic thiclo1ess gage used in this research are shown in Figures 1 through lOo The calibration of the gage is explained in Appendix 3. 21 Figure 1. Pneumatic Thickness Gage with Rotameter Connected 22 Figure 2o Isometric Viel'l of Pneumatic Thickness Gageo · I ------lo ------,, I .. f I . 1 I I I I I I I : -1 =rol~ I I I --r-~--.----( } .;.._"'VA I I 5 I -24~F-FIN. II i · l -e-1 16 = I - I I 11 !' = a, I ~la> ~Detail 'c' 1 I CD 1 1 1 1 Detail F (\J Detail H · ~Oetoil G --.--, - . C\I ...... N l I /Detail 'e' / / Detail 'A' DEPARTMENT OF CHEMICAL ENGINEERING' . MISSOURI SCHOOL OF MINES & METALLURGY ROLLA, MISSOl:JRI . ·PNEUMATIC THICKNESS GAGE · 11 FRONT VIEW RIGHT SIDE VIEW SCALE: I"= 6 DATE CASE NO: 60 DRAWN BY: 1H t / .. "l-60 FILE . NO: 490 . 1 CHECKED BY: ~" ~ N,~ (~ FIGURE NO: 3 APPROVED BY: ~U ~ Hc.«1 '6 o SHEET NO: I of 6 Aluminum 'Pi' Beam 7.. 7 11 ~<,--~~~~-a-a ~~~~~~1e I 1 1 1 .------Aluminum Pi ~ ,d'-24 NF-3 Fin. Hex. Beam Hd. Bolt Aluminum Inside Micrometer Steel Rod · ' .h0-32 Flot.Point Set ,_..,_..,._~--~--~----~----'-++-~...... ~H-A~:~ ..~~---i=i .. '[ Screw .f Lg. J" Drill -~~·x,"-24 NF-3 Fin. Hex. a Hd. Bolt ~10) rt) Beam & I =-Jv Detail 'E' - Full Scale --, 1 :.:-:;- DEPARTMENT OF CHEMICAL ENGINEERING & _t___ _ -- ., MISSOURI SCHOOL OF MINES & METALLURGY ,t. :::;- ROLLA, MISSOURI ~IN PNEUMATIC THICKNESS GAGE · FRONT VIEW 11 SCALE : la 11 3 DATE CASE NO: 6 0 DRAWN BY: 'r lf ...8L /-1/-(,0 FILE NO: 490 CHECKED BY: :/".r,J 2' /'441( '(..I') FIGURE NO: 4 APPROVED BY: P~o ?. HCA.,,, '6-,., SHEET NO· 2 of 6 I 8 11 ------"'M ~\ 111 -24 NF 16 1,~"----~-i~-2 ~- >I· . Hex. Hd. Bolt r----~------,,.r..,.c;-+--,,--~--- 5 .. 16 -24NF-Fin. = IU> Hex. Hd. Nut '°-t · ). ...5.\3"-24NF I 1s ·· Hex. Head Bolt U) t (\J f =-1 N =-1 N -----~--..__._,-·--1~ ~ (X) I J Detail 'F' LEG ADJUSTING SCREW Full Sc ale DEPARTMENT OF CHEMICAL ENGINEERING MISSOURI SCHOOL OF MINES & METALLURGY ROLLA, MISSOURI ·PNEl)MATIC THICKNESS GAGE RIGHT SIDE VIEW 11 SCALE: 1 = 3•• DATE CASE NO: 60 O~WN BY: 9~ -" I-JI -61) FILE NO: 490 CHECKED BY: /Jrv ~ fv/ ""f •b O FIGURE NO: 5 APPROVED BY: ~... !. fl-I ::;...,i 'b ~ SHEET NO: 3 of 6 ta" 7" 3" =tt>lv 7 ~· 16 ~1~ 28 61f'1 4 t t .r Oriti -,----,------.------, I " 11 I ~x 1 -24 NF-3 Fin. I 16 Hex. Hd. Bolt PANEL SUPPORTS 8-32 Fill. Hd.,· Cop See Detail 1 A1 Screw - 2 Lg. = 0 0 U) 0 0 @) ~---i------4-_J DEPARTMENT OF CHEMICAL ENGINEERING MISSOURI SCHOOL OF MINES & METALLURGY ROLLA, MISSOURI PNEUMATIC THICKNESS GAGE TOP VIEW SCALE: 1• • 3" DATE CASE NO: 60 DRAWN BY: J HA. /-~5-6-0 FILE NO: 4 90 CHECKED BY: (/)x, ~ M =I')_ I'° z CD -(/) Detail 'G' - Full Scale Drill a Counterbore Near Side ~ For 6- 32 Fill. Hd. Cop Screw DEPARTMENT OF CHEMICAL ENGINEERING 16 MISSOURI SCHOOL OF MINES & METALLURGY 7'' S·id,, .es ROLLA, MISSOURI 8 , Tap Center Portion For 8-32 :;: PNEUMATIC THICKNESS GAGE Fill. Hd. Cop Screw 5• Orlll a Counterbora Near Side f'or 8 - 32 1 1 16 Detail H - lsomettic View of Gage Arm Fill. Hd. Cap Screw SCALE: I"= 2• · DATE CASE NO: 60 DRAWN BY:,;, .. ~ •11-·0 FILE NO: 490 CHECKED BY: /J;-o ~ H~ t 60 FIGURE NO: . .1 APPROVED BY: /~ .~ J"/r,u.t ' 6-() SHEET NO: 5 of 6 28 Figure 80 Barrel Assembly Monnted in Gage Armo 29 Figure 9. Working Portion of Pneumatic Thickness Gage Disassembled. Listing from top to bottom: micrometer, air line adaptor from rota meter, aluminum. bearing, spring, barrel, nozzle, and panel support. 30. Aluminum Plug- Class 7 Flt . 980 11 8-52 Flat Point Set Screw 3" 16 Lg. Aluminum Aluminum ,_8-32 Fiii. Steel Hd. Cap Sere~ .£4 Lg. t =-Iv f f I Detail I o' - Air Line Adapter a-lro ______i______t 'iolv t DEPARTMENT OF CHEMICAL ENGINEERING Aluminum Plug MISSOURI SCHOOL OF MINES & METALLURGY Class 7 Fit ROLLA, MISSOURI PNEUMATIC THICKNESS GAGE Details 1C1 8 1D1 SCALE: Full DATE CASE NO: 60 8 D r-'-~ DRAWN BY: 1JI~ d-8-~0 FILE NO: 490 1 1 CHECKED BY : FIGURE NO: Detail C - Barrel Assembly ~ .3 M ~-·1 'bv I O Full Section APPROVED BY: ~o 3 /vfc_i,J. · bo SHEET NO: 6 of 6 31 Electrical Circuit. A transfonner with a capacity of 7500 volts was connected with t~ powerstats in series to an electrical line of no volts and 60 cycles. The purpose of the po.werstats was to regulate the input of electricity to the transfonner. Because a gradually increasing voltage was desired for the determination of the breakdown voltage, one powerstat was driven by a gear-in-head motor. The alten1ating current from the transformer was converted to direct current by means of two voltage rectifier tubes. Two condensers were placed in the circuit to remove any residual alteniating current. The measuring circuit used was a series of one megohm resistors acting as a voltage divider placed in series w.ith a recording potentiometer and arranged so that from one to five resistors could be used to increase or decrease the range of meas- urement. The calibration of the recording potentiometer was facilitated by the use of a portable potentiometer. By means of this a known number of millivolts was placed into the recording potentiometer and the latter adjusted to give the same scale reading. It is stated in the Brown Electronik Manual that a full scale deflection on the potentiometer requires a current of 1 milliamp in the range of Oto 100 millivoltso It followed from this that a resistance of 1000 volts/1 milliamp or l megohm was required to give a full scale deflection when the transformer output was 1000 volts. Similar circuits were used by Davis(S) and Oakes(l9) with accuracy considered to be plus or minus l! per cent. The circuit diagram is shown' in Figure 11. 32 110 V 60 eye. 5 I. P0\1Grstat II 1======::t 12 2. Transformor - 7500 Volts 6 3. Voltago RGctiflor TubG 183 · 4. ~ry-" Cells ( 1.5 Volt) 8 )- 5. Toggle Switch 7 7 8 '\ ' '\ '\ 6. Resistor - 500 ohm, 10% -,: ...... '\ Recorder 8 ...... ~,, ..,,- // 7. Condenser - 800.0 V, . 2 mfd ~.,,.,, II 10 I/ 8. Resistor-· t megohm, I \AJott, I °lo 8 I I I I JI- I 9. Resistor - 100 ohm, 1.0 % I 8 I J} 10. Banana Plug II. Probo ( High Voltage Lead) 12. Painted · Panel Figura II. Wiring Diagram for Eloc.trical Circuit 33 Method of Procedure Coating Steel Panels. All paints w~re well stirred and strained before useo The panels were prepared by washing w.i.th acetone ·to remove all oil, dust, and dirt that might have collected during storageo Using the Baker Film Applicator Blade in conjunction with the Gardner Auto matic Film Applicator (Figure 12), a wet paint film of sufficient thick ness was laid down on the panel to give approximately 0.8 mils dry film. The panel was placed on a level surface to dry. 34 Figure 12. Baker Film Applicator Blade and Gardner Automatic Film Applicator. 35 Determination of the Thickness of Dry Paint Films ~r.ith the Pneu matic Thickness Gageo The following procedure was developed for the use of the pneumatic thickness gage. 1. Acetone was used to ·remove all traces of oil, dust, and dirt on the steel panels. 2. The masonite template (Figure 15) was placed on the panel and secured with clamps (Figure 13). 3. Positions for 1 reference point and 25 thickness determinations ·were marked lightly with a sharp pencil by tracing the outer edges of the holes in the template. 4. The template was removedo 5. The rotameter was connected to the compressed air line. 6. The panel was placed so that the reference point ,-m.s located directly below the measuring head (nozzle) of the gage. 7. Using a 4-power magnifying glass and a good source of light, the micrometer was adjusted to the nearest OoOOl inch so that a rota mete:r reading was obtained in the upper one-half of the scaleo So The micrometer setting and rotameter reading for the reference point were recorded. 9. The panel was removed and reinserted with tlie first point for thickness determination located directly below the measuring head. 10. Using a 4-potrer magnifying glass and a good source of light, the micrometer was adjusted to the nearest 0.001 inch so that a rota meter reading was obtained in the upper one-half of the scale. ll. The micrometer setting and rotameter reading for the first position on the uncoated panel were recorded. 36 120 The remaining 24 positions were determined in the same mannero 13 o The air floJ·l was turned off o 140 The panel was removed and the pa.int film laid as described on page 330 150 After the paint film had dried, the positions \·,ere relocated following procedures 2, 3, and 4o 160 The paint film was removed from the panel at the reference point only, ,tlth a drop of solvent or paint remover and wiped cleano 17 o The rotameter was connected to the compressed air lineo 180 The panel was replaced in the gage follo,-r.i.ng procedure 60 19 o The micrometer· t-ias reset to the reading taken previously in procedure 80 200 The support legs for the gage ann were adjusted so.that the same rotameter reading as recorded in procedure 8 was obtainedo 21.o The panel was removed and re~serted ld.th the first position for thickness determination located directly below the measuring heado 220 With the micrometer set to va;Lues obtained in procedures 11 and 12, rota.meter readings of ·the painted panel were recordedo 230 The differences between the rotameter readings.as obtained in procedures ll, 12 and 22 were recorded as the dry film thickness at the predetermined positionso 240 The thickness values obtained in procedure 23 were verified by removing the paint film from the entire panel by means of paint remover and once again determining the rotameter readings on the bare panel at the predetermined positionso 37 25. The differences between the values as determined in procedures 24 and 22 were again recorded as the dry film thickness at the predeter mined positions. 38 Determination of the Breakdown Voltage. In order to roughly determine the voltage.that would be needed to.breakdown the paint films, the approximate thickness of the latter was.measured with the General Electric Thickness Gage and then the paint film was electrically broken down. In this way a rough correlation be~een the film thickness and the required breakdown voltage was found together with the number of one megohm resistors needed in the circuit to cover the voltage require ment. The following procedure was developed for voltage determinations. l. The amplifier of the recorder was turned on and allowed to warm up for 20 minutes. 2. The correct number of one megohm resistors was placed in the circuit (1 resistor for values up to 1000 volts, 2 for 2000, 3 for 3000, etc.). 3. The masonite template (Figure 15) was positioned on the coated steel panel and secure~ with clamps. 4. One fourth inch polished steel ball bearings were placed in each of the 25 holes in the template (Figure 13). 5. The ground clip was placed on a bare portion of the panel •. 6. For each determination, one ball b~aring was c~nnected by means of the ball bearing contact (Figure 15) to the source of power. 7. The cathode voltage of the lB3 tubes was turned on. 8. _The chart drive of the recorder was turned on. 9. The powerstats were turned on while set at zero. 10. The motor drive to the powerstats was turned on. 39 llo The motor drive and pouerstats ,vere turned off immediately upon breakdown which. was noted by an instantaneous reversal of the recorder peno A typical section of the chart paper is shown in Figure 140 12. The chart drive was turned off o 130 The powerstats were reset to zero for the next determination by reversing the direction of the drive motoro 140 The detenn.ination nwnber was indicated on the chart papero 150 The value in millivolts/2 for that determination was recordedo 160 This procedure was repeated for the 24 remaining positionso 40 Figure 13. Steel Panel with Masonite Template Clamped in Positiono Also showing ball bearings in place, ball bearing cap on position 19, and ground clip attached. 41 Figure 140 Section of Recorder Charto ..L ~ ·;-16 DRILL 16 -f CIRCULAR · - I ,ALUMINUM 1 -i I FILE-!i. ·DEEP 26-£DRILL 32 ··rr. I I .,I • "-JN . . ! / i lf)t(O 1_ Al , ------+ct+ I • It - i ''1 .. / # 6 NC-32 X J.: ! 4 I; . ROUND HEAD MACHINE SCREW lo+-i~-1" -----..1,JI -----. --r BALL BEARING CONTACT I Scale f I I BALL BEARING I -~N J.: BEARING CONT ACT I ft) •N I . i - MASONITE \ , TEMPLATE . i . I \ \ -~-+-+-+-+-----+8 ·-t-I -+-+-+-+-----+I I I I ffll• i I I I j ~ .. ~~~~~~~~~~~~~~~~~~~~~~...PAINT FILM +-+-+-+-+--- --;t- STEEL +-+-+-+-+-----;+-I I I I I lfll• PANEL ' I I I I '1• ARRANGEMENT OF EQUIPMENT -ON COATED STEEL PANEL +-+-+-+-+---~-t- Scale + Full Section i i i i i ~N I I DEPARTMENT OF CHEMICAL ENGINEERING I I MISSOURI SCHOOL OF MINES & METALLURGY ROLLA, MISSOURI .. MASONITE TEMPLATE and BALL BEARING CONTACT MASONITE TEMPLATE Scale 1• • 2• SCALE: QI ,wt•d DATE CASE NO: 60 DRAWN BY: 7fl.J/J. ~ -~()-,0 FILE NO: 490 cHecKEo aY: Jl>o -3 N Data and Results In the following section the data and results, confirmed by multiple tests and subjected to statistical analysis, are giveno The sample calculations are found on·pages 101 through 1070 The data and results for the va~ous primers, finishes, clear primer vehicles, and clear finish vehicles are given in Tables IV through XXXIo For the sake of easy comparison, the above results are sunnnarized in Tables X, XVII, XX.IV, and XXXIo In addition, all data on breakdown voltage versus dry film thickness are plotted in Figures 16 through 43. Again, for the sake of comparison, composite graphs are given in Figures 22, 29, 36, and 43. 44 TABLE IV Dielectric Strength of Vinyl Primer (Room Temperature 76°F Relative Humidity 31%) Test Micrometer Rotameter Reading D£t Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/m.il reference point 0.177 2.68 2.68 2.68 1. 0.176 2.45 1.85 2.48 0.60 0.63 0.62 4 40.0 3200 5.16 2. n 2.73 2.08 2.73 0.65 0.65 0.65 n 38.8 3100 4.76 3. " 2.75 2.10 2.75 0.65 0.65 0.65 II 43.8 3510 5.40 4. " 2.85 2.20 2.88 0.65 0.68 0.67 " ti 41.8 3340 4.98 5. 0.178 2.05 1.40 2.05 0.65 0.65 0.65 ti 42.5 3400 5.23 6. 0.177 1.95 1.25 1.95 0.70 0.70 0.70 39.8 3180 4.55 7. 0.178 2.40 1.50 2.43 0.90 0.93 0.92 5" 42.2 4220. 4.59 8. n 2.95 2.00 2.95 0.95 0.95 0.95 " 46.0 4600 4.84 9. " 2.48 1.65 2.50 0.83 0.85 0.84 4 ** 10. " 2.83 2.08 2.83 0.75 0.75 0.75 " 48.4 3870 5.16 11. 0.176 2.15 1.45 2.18 0.70 0.73 0.72 n 48.6 3890 5.40 12. 0.178 1.75 1.05 1.78 0.70 0.73 0.72 5 35.6 3560 4.95 13. " 2.15 1.55 2.15 Oo60 0.60 0.60 n 28.3 2830 4.72 14. " 1.60 1.10 1.63 0.50 0.53 0.52 4 ** 15. " 2.13 1.80 2.15 0.33 0.35 0.34 " 21.2 1690 4.97 16. 0.176 1.88 1.15 1.88 0.73 0.73 0.73 n 48.4 3870 5.30 17. 0.177 2.25 1.25 2.25 1.00 1.00 1.00 5 49.6 4960 4.96 18. 2.65 1.90 . 2.68 0.75 0.78 0.77 " 35.5 ·3550 4.62 19. 0.178" 2.03 1.23 2.03 0.80 o.so 0.80 40.8 4080 5.lo 20. n 1.78 1.00 1.80 · 0.78 o.so 0.79 4" -37.0 2960 3.74 21. 0.175 2.75 1.65 2.78 1.10 1.13 1.12 ** 22. 2.80 1.85 2.83 0.95 0.98 0.97 5" 23. " 2.98 2.08 2.98 0.90 0.90 0.90 46.8*** 4680 5.20 24. 0.177" 2.28 1.70 2.28 o.58 0.58 0.58 " 26.4 2640 4.55 25. 0.178 2.15 1.50 · 2.15 0.65 0.65 0.65 4" 40.3 3220 4.95 ** - no breakdown occurred *** - recorder standardizing during breakdown 45 TABLE V Dielectric Strength of Chlorinated Rubber Primer (Room Temperature 75°F Relative Humidity 25%) Test Micrometer Rotameter Readjng D!:t Film Thickness Average Resistance Breakdotin Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mi.ls mils mils mils megohms mv/2 volts kv/mil reference point 0.176 2.60 2.60 2.60 1. 0.174 2.40 1.90 2.40 0.50 o.so 0.50 5 10.2 1020 2.04 2. 2.90 2.40 2.90 0.50 0.50 0.50 ti 5.6 560 1.12 3. 0.175" 2.10 1.55 2.10 0.55 0.55 0.55 ti 10.3. 1030 1.87 4. " 1.60 0.90 1.60 0.70 0.70 0.70 rt 13.0 1300 1.86 5. 0.177 2.55 1.70 2.58 0.85 0.88 0.87 " 5.2 520 0.60 6. 0.174 2.23 1.60 2.25 0.63 0.65 0.64 12.7 1270 1.98 7. 0.176 1.80 1.15 1.83 0.65 0.68 0.67 n" 10.3 1030 · 1.54 8. n 2.30 1.45 2.30 0.85 0.85 0.85 " 17.4 1740 2.04 9. " 1.35 0.55 1.38 o.so 0.83 0.82 " 15.6 1560 1.90 10. " 2.65 1.90 2.65 0.75 0.75 0.75 fl 10.8 1080 1.44 ll. 0.175 1.55 0.95 1.53 0.60 0.58 0.59 ti 13.8 1380 2.34 12. " 2.88 2.05 2.85 0.83 0.80 0.82 " 18.5 1850 2.26 · 13. 0.176 2.48 1.65 2.48 0.83 0.83 0.83 " 15.7 1570 1.89 14. " 1.60 0.70 1.60 0.90 0.90 0.90 " 20.5 2050 2.28 15. " l.93 1.30 1.93 0.63 0.63 0.63 " 10.0 1000 1.59 16. 0.174 2.50 1.75 2.50 0.75 0.75 0.75 12.4 .1240 l.65 17. 2.88 1.83 2.88 1.05 1.05 1.05 " 22.6 2260 2.15 18. 0.175" 2.25 1.50 2.28 0.75 0.78 0.77 " 11.8 1180 1.53 19. . " 1.88 1.25 1.90 0.63 0.65 0.64 n" 10.8 1080 1.69 20. 0.176 2.18 1.45 2.20 0.73 0.75 0.74 " 13.4 1340 1.81 21. 0.174 2.28 1.50 2.25 0.78 0.75 0.77 " 17.2 1720 2.23 22. " 2.18 1.45 2.13 0.73 0.68 0.71 " 11.2 1120 1.58 23. " 2.48 1.63 2.48 0.85 0.85 0.85 n 12.4 1240 1.46 24. tt 2.18 1.28 2.18 0.90 0.90 0.90 " 24.0 2400 2.67 25. 0.175 2.15 1.35 2.15 0.80 0.80 o.so " 16.5 1650 2.06 46 TABLE VI Dielectric Strength of Epoxy Ester Pr~r (Room Temperature 78°F Relative Humidity 27%) Test Micrometer Rotameter Readi nH D£t Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.111 2.18 2.18 2.18 l. 0.175 1.85 1.38 1.85 0.47 0.47 0.47 2 15.3 . 610 1.30 2. tt 2.43 1.85 2.45 o;58 0.60 0.59 II 18.4 740 1.25 3. 2.10 2.15 2.73 0.55 0.58 0.57 II 17.4 700 1.23 4. "It 2.08 1.53 2.10 0.55 0.57 0.56 ti 24.8 990 1.77 s. 0.178 2.35 1.20 2.30 1.15 1.10 lol3 n 47.5 1900 1.68 6. 0.175 1.68 1.50 1.75 0.18 0.25 II 29.3 ll70 1. 0.176 2.48 1.83 2.50 0.65 0.67 0.66 It 22.0 880 1.33 8. It 2.75 2.05 2.80 0.70 . 0.75 0.73 fl 18.8 750 1.03 9. II 1.80 · 1.25 l..85 0.55 0.60 0.58 It 16.3 650 1.12 10. 0.111 2.25 1.78 2.30 0.47 0.52 0.50 n ll.4 455 0.91 ll. 0.175 2.20 1.90 2.20 0.30 0.30 0.30 n 8.6 345 1.15 12. 0.176 2.43 1.80 2.45 0.63 0.65 0.64 It 17.7 710 l.ll 13. 0.177 2.05 1.40 2.13 0.65 0.73 tt 26.2 1050 14. It 1.00 0.48 l..03 0.52 0.55 0.54 It 10.8 430 0.80 15. It 1.53 1.35 1.55 0.18 0.20 0.19 It 12.3 490 2.58 16. o.175 2.05 1.85 2.03 0.20 0.18 0.19 It 17. 2.43 2.25 2.43 0.18 0.18 0.18 n.o** 440 2.44 18. "II 2.95 2.65 2.95 0.30 0.30 0.30 " 9.5 ·380 1.27 19. · n 2.75 2.25 2.75 0.50 0.50 0.50 "tt 15.6 620 1.24 20. 0.177 1.95 1.55 1.93 0.40 0.38 0.39 It 12.a 510 1.31 21. 0.175 1.75 1.53 1.75 0.22 0.22 0.22 It 2.8 no 0.50 22. ti 1.80 1.63 l..80 0.17 0.17 0.17 tt 10.8 430 2.53 23. ti 2.03 1.80 2.03 0.23 0.23 0.23 10.0 400 1.74 24. tt 1.63 1.43 1.65 0.20 0.22 0.21 II" 7.8 310 1.47 25. ft 2.75 2.55 2.75 0.20 0.20 0.20 " 5.6 225 1.13 ** - no breakdol1!l occurred TABLE VII 47 Dielectric Strength of Alkyd Primer (Room Temperature 76°F Relative Humidity 31%) Test Micrometer Rotameter Reading Dr.r Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils . mils mils megohms mv/2 volts kv/mi.l reference point 0.177 2.55 2.55 2.55 1. 0.176 1.80 1.50 1.83 0.30 0.33 0.32 l 33.2 665 2.08 2. 2.20 1.85 2.20 o·.3s 0.35 0.35 13.4 298 0.77 3. "ft 2.45 2.10 2.48 0.35 0.38 0.37 "ft 37.0 740 2.00 4. ft 2.15 1.90 2.18 0.25 0.28 0.27 n 25.3 505 1.80 5. ft 2.53 2.25 2.53 0.28 0.28 0.28 It 28.4 568 2.03 6. 0.177 2.33 1.53 2.33 0.80 0.80 0.80 26.2 525 0.66 7. 2.58 1.75 2.s8 0.83 0.83 0.83 "2 47.2 1890. 2.28 8. "ft 1.75 1.85 2.75 0.90 0.90 0.90 3 29.0 1740 l.93 9. 0.178 2.43· 1.48 2.43 0.95 0.95 0.95 fl 30.0 1800 1.90 10. n 2.23 1.45 2.23 0.78 0.78 0.78 11 30.4 1820 2.34 ll. 0.177 1.95 1.10 1.95 o.85 0.85 o.85 32.5 1950 2.29 12. 2.10 1.35 2.13 0.75 0.78 0.77 "n 29.8 1790 2.32 13. "n 2.20 1.35 2.23 0.85 0.88 0.81· 14. 0.178 2.15 1.15 2.15 1.00 1.00 1.00 n" 38.6* 2320 2.32 15. " l.95 1.20 1.95 0.75 0.75 0.75 II 2s.2 1510 2.01 16. 0.175 2.80 2.05 2.80 0.75 0.75 0.75 n 26.6 1600 2.13 17. 2.85 2.25 2.85 0.60 0.60 0.60 n 17.8 1070 l.78 18. 0.176" 2.30 1.50 2.30 0.80 0.80 o.so n 29.5 1770 2.21 19. . rt 2.53 2.03 2.53 o.so o.so 0.50 4 11.3 905 1.81 20. n 2.75 2.15 2.78 ·0.60 0.63 0.62 3 19.2 1150 1.85 21. 0.175 2.65 1.95 2.68 0.70 0.73 0.72 n 25.0 1500 2.oa 22. 2.70 2.15 2.73 0.55 0.58 0.57 n 18.0 1080 1.90 23. "n 2.73 2.20 2.73 0.53 0.53 0.53 n 17.2 1030 1.94 24. " 2.45 1.95 2.45 o.so o.so 0.50 t1 18.5 1110 2.22 25. 11 2.95 2.so 2.98 0.45 0.48 0.47 " 18.3 1100 2.32 * - powerstat not reset to zero 48 TABLE VIII Dielectric Strength of Oil Prime~ (Room Temperature 80°F Relative Humidity 41%) Test Micrometer Rotameter Readin~ Dr! Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thiclmess in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.23 2.23 2.23 1. 0.176 1.90 1.15 1.90 0.75 0.75 0.75 2 26.4 1060 1.41 2. " 2.15 1.35 2.13 0.80 0.78 0.79 u 24.8 990 1.25 3. " 2.15 1.33 2.13 0.82 0.80 0.81 " 13.9 555 0.68 4. " 2.10 1.60 2.13 o.so 0.53 0.52 n 22.8' 910 1.75 5. 0.177 2.48 1.65 2.48 0.83 0.83 0.83 fl 28.6 1140 1.37 6. 1.65 o.so 1.63 1.15 1.13 1.14 35.6 1420 1.24 7. " 3.00 1.60 3.00 1.40 1.40 1.40 " 40.2 1610 1.15 8. 0.178" 2.45 1.00 2.45 1.45 1.45 1.45 " 41.8 1670 1.15 9. 1.85 1.08 1.85 0.77 0.77 0.77 " 31.8 1270 1.65 10. "n 2.33 1.60 2.33 0.73 0.73 0.73 "n 19.3 770 1.05 ll. 0.176 1.73 0.95 1.73 0.78 0.78 0.78 32.0 1280 1.64 12. 0.177 2.so 1.33 2.50 1.17 1.17 1.17 " 34.0 1360 1.16 13. n 3.00 1.83 3.00 1.17 1.17 1.17 "n 41.4 1660 1.42 14. 2.40 1.70 2.40 0.70 0.70 0.70 ti 7.0 280 0.40 15. "n 3.05 2.50 3.03 0.55 0.53 0.54 n 12.0 480 0.89 16. 0.176 1.50 0.88 1.50 0.62 0.62 0.62 23.0 920 1.48 17. n 2.65 1.75 2.65 0.90 0.90 0.90 " 35.0 ·1400 1.55 18. 0.177 2.40 1.48 2.43 0.92 0.95 0.94 "n 26.0 -1040 l.ll 19. n 2.65 2.20 2.65 0.45 0.45 0.45 27.1 1080 2.40 20. n 2.13 1.98 ~13 . 0.15 0.15 0.15 "n . 6.2 250 1.66 21. 0.175 1.95 1.65 1.98 0.30 0.33 0.32 n 7.6 300 0.94 22. 11 2.20 1.85 2.18 0.35 0.33 0.34 " 9.6 380 1.12 23. " 2.53 2.13 2.50 0.40 0.37 0.39 7.0 280 0.72 24. 0.177 2.20 1.75 2.20 0.45 0.45 0.45 It" 16.0 640 1.42 25. " 2.75 2.60 2.75 0.15 ·0.15 0.15 ti 6.7 270 1.80 49 TABLE LX Dielectric Strength of Phenolic Pr~er {Room Temperature 81°F Relative Hwnidity 41%) Test Micrometer Rotameter Reading Dr!: Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) {A-B) (C-B) inches mils mils mils ·mils mils mils megohms mv/2 volts kv/mil reference point 0.177 1.70 1.70 1.70 1. 0.174 2.58 2.10 2.55 0.48 0.45 0.47 1 15.2 304 0.65 2. 0.175 2.00 1.55 2.00 0.45 0.45 0.45 n 12.3 248 0.55 3. ft 2.30 1.70 2.21 0.60 0.57 0.59 " 31.1 622 1.05 4. " 1.65 1.20 1.63 0.45 0.43 0.44 " . 26.5 530 1.20 5. 0.177 2.83 1.80 2.83 1.03 1.03 1.03 n ** 6. 0.174 2.38 2.20 2.38 0.18 0.18 0.18 o.o 7. 0.176 2.08 1.45 2.08 0.63 0.63 0.63 "n 18.2 364 o.58 8. " 2.40 1.65 2.43 0.75 0.78 0.77 n 24.0 480 0.62 9. n 1.45 0.95 1.47 0.50 0.52 0.51 " 33.3 668 1.31 10. It 2.83 2.33 2.83 0.50 0.50 0.50 " 20.5 410 0.82 11. 0.174 2.83 2.58 2.83 0.25 0.25 0.25 6.8 136 0.54 12. 0.176 1.95 1.35 1.95 0.60 0.60 0.60 "n 34.8 695 1.16 13. " 2.75 1.90 2.77 0.85 0.87 0.86 " 26.7 535 0.62 14. " 1.53 1.05 1.55 0.48 0.50 0.49 " 25.3 505 l.03 15. " 2.10 1.80 2.10 0.30 0.30 0.30 It 14.0 280 0.93 16. 0.174 2.65 2.45 2.65 0.20 0.20 0.20 " 7.3 146 0.73 17. 0.175 2.00 1.55 2.00 0.45 0.45 0.45 " 12.6 250 0.55 18. It 2.55 1.98 2.55 0.57 0.57 0.57 " 19.0 380 0.67 19. . It 2.25 1.65 2.25 0.60 0.60 0.60 " 14.0 280 0.47 20. 0.176 2.58 2.00 2.55 0.58 0.55 0.57 " 36.4 730 1.28 21. 0.174 2.50 2.10 2.47 0.40 0.37 0.39 11.0 220 0.56 22. n 2.55 1.93 2.55 0.62 0.62 0.62 " a.a 176 0.29 23. 2.75 2.13 2.77 0.62 0.64 0.63 " 16.5 330 0.52 24. "n 2.30 1.88 2.30 0.42 0.42 0.42 ft" 20.2 405 0.96 25. 0.175 2.43 1.95 2.43 0.48 0.48 0.48 " 16.0 320 0.67 ** - no breakdown occurred 50 TABLE X Comparison of Results of Primers Table Type of Coating No. Correlation Equation of the Variance about No. of Coefficient Regression Line Regression Line Tests r volts IV vinyl 20 0.97 y = 5000x - 10 400 v chlorinated rubber 24 0.82 y = 2700x - 580 . 530 VI epoxy ester 18 0.92 y = 1500x - 75 320 VII alkyd 22 0.98 . y = 2300x - 130 220 VIII oil 21 0.84 y = l200x - 50 600 IX ph~o~ic 23 0.49 y = 570x - 100 330 51 5000 I I 4000 rJl ~ 0> ~ 3000 ~ ~ ~ ..,:...~ 0 2000 iCQ 1000 I 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKN~S, MILS FIGURE 16 • . BREAKDOWN VOLTAGE VERSUS AVERAGE FILM THICKNESS: VINYL PRIMER. 52 5000 4000 0~ > 3000 2000 l.000 / / / / 1/ 0 0.2 0.4 0.6 0.8 1.0 L2 1.4 FILM TIIlCKNESS, illLS F·IGURE 17. · BREAKDOWN VOLTAGE VERSUS AVERAGE Flill THICKNESS CHLORINATED ROBBER PRIMER. 53 sooo L· 4000 1000 / 0 / / if}o /o/ / / / Op"' / / 0 0 0.2 0.4 0.6 0.8 1.0 1~2 1.4 J7IW TlllOillESSp HILS FIGURE 18• . .mmAKllmffl VOLTAGE VERSUS AVERAGE FIIli TlllcmIESS: EPOXY F3TER PRmEft. 54 / / / / / / 1000 / / / / / / / / / 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 JlIGtmE 19. · B!iEAKDOl$J VOLTA.OE Vm!SUS AVERMm Fiil! fflI~: ALKYD mruu. 55 5000 4000 0~ > 3000 0 1000 0 ,,,./ _.... 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FIU1 THiomESS, llILS 17IOmm 20 • . BREAKDOtJN VOL'i'AOO VImSUS AVERAGE nm THIOOmss: OIL PRnmt. 56 5000 I~ i 4000 Cl) E-4 H 0 > .... 3000 ~ 9 ~ Hg $ 8 I 2000 1000 ------o-~------00~-o .-----;::--..o------a>o o'- 0 e - o o . _o--- 0 -- 0 0.2 0.4 0.6 o.a 1.0 1.2 1.4 FILM THICKNESS, MILS FIGURE 21.. BREAKDOt1N VOLTAGE VERSUS AVERAGE FILM THICKNESS: PHEI'WLIC PRIMER. 57 5000 Vinyl 4000 r)l E-i H ~ 9\ 3000 ~ ti ~ ~ Alkyd Chlorinated 2000 Rubber · IC:) Epoxy Ester Oil 1000 Phenolic 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKNESS, MILS FIGURE 22. COMPAIUSON OF BREAKDO\iN VOLTAGE VERSUS AVERAGE FIIli THICKNESS FOR THE VARIOUS PRIMERS. ss· TABLE XI Dielectric Strength of Vinyl Finish {Room·Temperature 76°F Relative Humidity 44%) Test Micrometer Rotameter Reading D!:f: Film Thickness Average Resistance Breakdown Voltage Dielectric Noo Setting before after after paint Thickness in Circuit recorp.ed calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megoluns mv/2 . volts kv/mil reference point 0.175 2,75 2.78 2. 75 1. Ool75 1.80 1.53 1.80 0.27 0.27 0.27 3 15.2 912 3.38 2. " 1.95 1.73 1.98 0.22 Oo25 0.24 " 12.8 768 3.20 3. n 1.15 0.90 1.18 0.25 0.28 0.27 " 16.4 984 3.64 4. " 1.73 1.35 1.75 0.38 0.40 0.39 " 33.5 2010 5.15 s. " 1.60 1.28 1.63 0.32 0.35 0.34 11 21.5 1290 3.80 6. Ool76 1.95 L45 1.95 0.50 a.so 0.50 n · 27.0 1620 3.24 7. " 2.13 1.60 2.15 0.53 0.55 0.54 " 41.8 2510 4.65 8. " 1.18 0.73 1.20 0.45 0.47 0.46 It 45.2 2712 5.88 9. n 1.48 1.00 1.50 0.48 0.50 0.49 " 44.1 2646 5.40 10. 11 1.40 1.00 1.43 0.40 0.43 0.42 n 27 oO 1620 3.a6 11. n 1.80 1.30 1.83 0.50 0.53 0.52 n 37.5 2250 4.32 12. n 1.95 1.43 1.98 0.52 0.55 0.54 " 41.8 2510 4.65 13. " 0.90 0.35 0.90 0.55 o.ss 0.55 rt 10.7 . 640 1.16 14. n 1.15 0.73 1.15 0.42 0.42 0.42 " 29.6 1776 4.22 15. n 1.38 0.95 1.40 0.43 Oo45 Oo44 " 29.5 1770 4.02 16. 0.174 2.40 2.os 2.40 Oo35 0.35 0.35 n 28.4 1700 4.85 17. n 2.65 2.30 2.65 0.35 0.35 0.35 " 23.4 1400 4.00 18. 2.45 2.00 2.48 Oo45 0.48 0.47 It 35.0 2100 4.47 19. o.175" 2.10 1.70 2.13 0.40 0.43 0.42 n 24,6 1476 3.51 20. " 1.55 L33 1.55 0.22 0.22 0.22 " 2006 1236 5.60 21. 0.173 2.20 2.05 2.20 0.15 0.15 0.15 n 9.2 552 3.68 22. " 2.so 2.35 2.50 0.15 · 0.15 0.15 " 15.l 906 6.04 23. n 2.15 i.95 2.15 0.20 Oo20 0.20 " 706 456 2.28 24. " 2.83 2.63 2.80 0.20 0.17 0.19 n 11.0 660 3.47 250 " 2.75 2.60 2.75 0.15 OolS 0.15 n 7.8 468 3.12 59 TABLE XI (continued) Dielectric Strength of Vinyl Finish (Room Temperature 76°F Relative Humidity 44%) Test Micrometer Rotameter Reading D£t Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Settlllg before after after paint Thickness in Circuit recorcled calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B} inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.175 2.65 2.65 2.65 l. 0.174 2.53 1.88 2.53 0.65 0.65 0.65 5 22.1 2210 3.38 2. tr 2.78 2.05 2.75 0.73 0.70 0.72 27.5 2750 3.82 3. 1.90 1.25 1.93 0.65 0.68 0.67 " 24.2 2420 3.58 4. " 2.45 1.70 2.45 0.75 0.75 0.75 "tr 37.8 3780 5.07 5. "tr 2.33 1.58 2.35 0.75 0.77 0.76 u 22.2 2220 2~90 6. 0.175 2.65 1.75 2.65 0.90 0.90 0.90 " 10.6 1060 1.17 7. n 2.83 1.90 2.85 0.93 0.95 0.94. " 36.8 3680 3.94 8. " 1.80 0.95 lo83 o.85 0.88 0.87 ft 38.5 3850 4.43 9. " 2.15 1.23 2.15 0.92 0.92 0.92 tr 34.4 3440 3.75 10. " 2.05 1.23 2.08 0·.82 0.85 0.84 tt 27.6 2760 3.28 11. u 2.55 1.63 2.55 Oo82 0.82 0.82 n 41.8 4180 5.12 12. " 2.65 1.68 2.65 0.97 0.97 0.97 " 36.5 3650 3.76 13. tr 1.43 0.60 1.45 0.83 0.85 0.84 " 37.9 3790 4.52 14. " 1.83 1.03 1.85 o.ao 0.82 0.81 n 38o0 3800 4.69 15. " 2.03 1.10 2.03 0.93 0.93 0.93 " 39.6 3960 4.25 16. 0.174 2.os 1.38 2.03 0.67 0.65 0.66 n 33.4 3340 5.07 17. n 2.33 1.55 2.30 0.78 0.75 0.77 ft 26.0 2600 3.38 18. tr 2.10 1.25 2.10 0.85 0.85 0.85 26.8 2680 3.18 19. 0.175 1.75 0.95 1.73 o.ao 0.78 0.79 "n 16.1 1610 . 2.02 20. 0.174 2.38 1.58 2.35 0.80 0.77 0.79 " 2.9.8 2980 ·3.80 21. 0.173 1.93 1.33 1.90 0.60 o_.57 0.59 27.4 2740 4.66 22. ti 2.15 1.55 2.10 0.60 0.55 0.58 " 17.0 1700 2.93 23. ti 1.80 1.15 1.83 0.65 0.62 0.64 "n 30.0 3000 4.69 24. " 2.50 1.83 2.50 0.67 0.67 0.67 u 19.0 1900 2.84 25. " 2.45 1.75 2.45 0.70 0.70 0.70 " 26.7 2670 3.78 60 TABLE XII Dielectric Strength of Chlorinated Rubber Finish (Room Temperature so°F Relative Humidity 29%) Test Micrometer Rota.meter Readjng Drl: Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thiclmess in Circuit recorded calculated Strength painting painting removal (A) (B) (C). (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv(mil reference point 0.175 2.05 2.05 2.05 1. 0.174 1.85 1.63 1.85 0.22 0.22 0.22 5 3.8 380 1.73 2. " 2.35 2.10 2~36 0.25 0.25 0.25 " 5.4 540 2.16 3. " 2.65 . 2.38 2.68 0.27 0.30 0.29 II 6.6 660 2.21 4. n 2.03 1.75 2.05 0.28 0.30 0.29 " 6.2 620 2.14 5. 0.177 2.30 1.45 2.30 0.85 0.85 0.85 " 13.8 1380 · 1.62 6. 0.173 2.60 2.60 2.60 o.oo o.oo o.oo " o.o 7. 0.175 2.40 1.98 2.40 0.42 0.42 0.42 · " 9.1 910 2.16 8. tr 2.10 2.25 2.70 0.45 0.45 0.45 " 8.6 860 1.91 9. 1.75 1.43 1.78 0.32 0.35 0.34 6.8 680 2.00 . 10. 0.176" 2.10 1.85 2.13 o.·25 9.28 0.27 "n 8.3 830 3.07 ll. 0.174 2.15 2.05 2.15 0.10 0.10 0.10 " 2.0 200 2.00 12. 0.175 2.30 1.88 2.30 0.42 0.42 0.42 " 9.6 960 2.28 13. 0.176 2.05 1.50 2.08 0.55 0.58 0.57 " ll.6 1160 2.04 14. 0.175 1.85 1.50 1.85 0.35 0.35 0.35 n 7.6 760 2.17 15. " 2.50 · 2.25 2.50 0.25 0.25 0.25 " 2.8 280 1.12 16. 0.174 . 1.90 1.85 1.90 0.05 0.05 0.05 n o.o 17. II 2.40 2.10 2.40 0.30 0.30 0.30 It 5.5 550 1.83 18. 2.88 2.60 2.90 0.28 0.30 0.29 6.0 600 ·2.07 19. "II 2.65 2.25 2.68 0.40 0.43 0.42 II" 7.5 750 1.78 20. 0.175 2.90 2.60 2.90 0.30 · 0.30 0.30 " .8.0 800 2.66 21. 0.174 1.83 1.65 1.85 0.18 0.20 0.19 " o.o 22. " 1.85 1.55 1.85 0.30 0.30 0.30 " 4.6 460 1.53 23. " 2.05 1.70 2.05 0.35 0.35 0.35 11 5.0 500 1.43 24. " 1.63 1.43 1.65 0.20 0.22 0.21 11 5.4 540 2.57 25. " 2.so 2.53 2.80 0.21 0.27 0.27 11 2.6 260 0.96 61 TABLE XIII Dielectric Strength of Epoxy Ester Finish (Room Temperature 78°F Relative Humidity 27%) Test Micrometer Rotameter Readj D£ Dr.t Film Thickness Average Resistance Breakdo"WD. Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.55 2.55 2.55 1. 0.176 1.95 1.58 1.90 0.37 0.32 0.35 3 10.0 600 1.71 2. 2.25 1.93 2.25 0.42 0.42 0.42 n 6.8 410 0.97 3. n" 2.55 2.20 2.50 0.35 0.30 0.33 rt 8.6 515 1.56 4. " 2.33. 2.05 2.33 0.28 0.28 0.28 " 6.6 395 1.41 5. n 2.75 2.43 2.75 0.32 0.32 0.32 " 7.8 470 1.47 6. ·0.111 2.43 1.50 2.40 0.93 0.90 0.92 n 17.2 1030 1.12 7. rt 2.s8 1.75 2.58 0.83 0.83 0.83 " 16.4 985 1.18 a. " 2.73 l.90 2.75 0.83 o.a5 0.84 " 38.2 2290 2.12 9. 0.178 2.45 1.48 2.45 0.97 0.97 0.97 " 27.0 1620 1.67 10. n 2.23 1.40 2.20 0.83 9.ao 0.82 " 35.3 2120 2.59 ll. 0.177 1.90 1.10 1.93 0.80 0.83 0.82 38.2 2290 2.79 12. 2.05 1.30 2.os · 0.75 0.75 0.75 " 25.7 1540 2.05 13. "n 2.13 1.38 2.15 0.75 0.77 0.76 "n 38.2 2290 3.01 14. Ool78 2.05 1.20 2.os 0.85 0.85 0.85 n 44.5 2670 3.14 15. ft 1.90 1.10 1.90 0.80 0.80 0.80 " 20.0 1200 1.50 16. 0.175 2.73 2.10 2.73 0.63 0.63 0.63 n 21.8 1310 2.os 17. II 2.80 2.25 2.80 0.55 0.55 0.55 ti 16.4 985 1.79 18. 0.176 2.2s 1.58 2.25 0.67 0.67 0.67 26.0 1560 2.33 19. tr 2.85 2.23 2.85 0.62 0.62 0.62 "ti 25.8 1550 2.50 20. " 2.68 2.15 2.70 0.53 . 0.55 0.54 " .iH~ 21. 0.175 2.63 2.08 2.65 0.55 0.$7 0.56 " 17.4 1045 1.87 22. " 2.65 2.25 2.68 0.40 0.43 0.42 " 16.6 995 2.37 23. n 2.8s 2.30 2.88 o.ss 0.58 0.57 " 24.0 1440 2.53 24. " 2.53 2.25 2.53 0.28 0.28 0.28 ti 10.2 610 2.18 25. " 3.00 2.70 3.05 0.30 0.35 0.33 n 11.7 700 2.12 *** - recorder standardizing during breakdown 62 TABLE XIV Dielectric Strength of Alkyd Finish (Room Temperature 79°F Relative Hwnidity 37%) Test Micrometer Rotameter Reading D~ Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Setting before after ·after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (c) (A-B) (C-B) inches mils mils mils mi.ls mils mils megohms mv/2 volts kv/mi.l reference point 0.176 2.05 2.03 2.05 1. 0.175 2.05 1.55 2.05 0.50 0.50 0.50 2 11.0 440 0.88 2. " 2.28 1.75 2.30 0.53 0.55 0.54 .. 14.4 576 1.06 3. u 1.38 0.95 1.38 0.43 0.43 0.43 " 9.8 392 0.91 4. " 1.85 1.28 1.85 0.57 0.57 0.57 .. 15.6 625 1 •.10 5. n 1.85 1.28 1.85 0.57 0.57 0.57 " 15.0 600 1.05 6. 0.176 2.23 1.20 2.23 1.03 1.03 1.03 " 8.8 352 0.34 7. n 2.30 1.38 2.33 0.92 0.95 0.94 " 11.8 472 0.50 8. 11 1.40 0.53 1.43 0.87 0.90 0.89 " 11.4 456 0.51 9. u 1.65 0.78 1.65 0.87 0.87 0.87 " 9.4 376 0.43 . 10. 11 1.60 0.75 1.63 0.85 0.88 0.87 " 13.7 548 0.63 11. 2.05 1.00 2.05 1.05 1.05 1.05 ti 14.5 580 0.55 12. " 2.13 1.10 2.13 1.03 1.03 1.03 14.0 560 0.54 13. "u 0.95 0.15 0.97 0.80 0.82 0.81 " 9.3 372 0.46 14. n 1.35 0.50 1.35 0.85 0.85 0.85 "n 16.l 644 0.76 15. 11 1.50 0.70 1.50 0.80 0.80 0.80 " 15.9 636 0.79 16. 0.175 1.60 0.88 1.63 0.72 0.75 0.74 9.2 368 0.50 17. 1.78 1.03 1.80 0.75 0.77 0.76 " 10.3 412 0.54 18. "u 1.55 0.80 1.55 0.75 0.75 0.75 " 10.0 400 0.53 19. u 2.25 1.40 2.28 0.85 0.88 0.87 ".. 11.0 440 0.51 20. " 1.78 1.15 1.78 0.63 0.63 0.63 n a.a 352 0.56 21. 0.173 2."45 2.08 2.45 0.37 0.37 0.37 " 5.2 208 0.56 22. " 2.10 2.25 2.70 0.45 0.45 0.45 " 5.6 224 o.so 23. tt 2.30 1.95 2.30 0.35 0.35 0.35 " 4.7 188 0.54 24. " 2.95 2.63 2.95 0.32 0.32 0.32 " 4.0 160 o.so 25. " 2.93 2.63 2.95 0.30 0.32 0.31 It 2.3 92 0.30 63 TABLE XV Dielectric Strength of Oil Finish {Room Temperature 76°F Relative Humidity 25%} Test Micrometer Rotameter Reading D~ Film Thiclmes§ Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C). (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.08 2.08 2.08 1. 0.174 l.78 1.55 1.83 0.23 0.28 0.25 l 9.8 195 0.78 2. n 2.40 2.18 2·.45 0.22 0.27 0.25 n 10.6 210 0.84 3. " 2.43 2.05 2.43 0.38 0.38 0.38 11 9.3 185 0.49 4. " 2.75 2.30 2.75 0.45 0.45 0.45 11 16.3 325 0.72 5. 0.175 2.33 1.75 2.33 0.58 0.58 0.58 " 21.2 425 0.72 6. 0.174 2.05 1.85 2.os 0.20 0.20 0.20 n 5.0 100 0.50 n 7. 2.70 2.43 2.75 0.27 0.32 0.30 ~ ~ ..· 11.3 225 0.75 8. n 3.00 2.53 3.00 0.47 0.47 0.47 12.3 245 0.52 9. 0.175 2.30 1.60 2.30 0.70 0.70 0.70 n" 22.4 450 0.64 . 10. , n 2.93 2.25 2.93 0.68 0.68 0.68 n 25.7 515 0.76 n. " 2.30 1.50 2.30 0.80 0.80 0.80 rt 23.6 470 0.59 12. ti 2.95 2.08 2.95 0.87 0.87 0.87 n 27.0 540 0.62 13. 0.176 2.20 1.15 2.20 1.05 1.05 1.05 n 34.5 690 0.66 14. " 2.35 1.20 2.35 1.15 1.15 1.15 tt 29.4 590 0.51 15. 0.177 2.05 0.85 2.05 1.20 1.20 1.20 " 34.2 685 0.57 16. 0.175 1.93 1.35 1.98 0.58 0.63 0.60 n 26.4 530 0.88 17. 11 2.53 1.78 2.53 0.75 0.75 0.75 n 23.0 460 0.61 18. II 2.78 1.90 2.78 0,88 0.88 0.88 tr 34.0 680 0.77 19. n 2.73 1.85 2.73 0.88 0.88 0.88 " 23.4 470 ·o.53 20. 0.176 2.48 1.38 2.48 1.10 1.10 1.10 " 32.0 640 0.58 21. 0.175 1.83 0.98 1.83 0,85 0.85 0.85 tr 26.5 .525 0.62 22. II 2.23 1.35 2.23 0.88 0.88 0.88 29.8 595 0.68 23. n 2.13 1.20 2.18 0.93 0.98 0.95 "ft 37.0 740 0.78 24. n 2.45 1.40 2.45 1.05 1.05 1.05 tr 38.3 765 0.73 25. II 2.78 1.68 2.78 1.10 1.10 1.10 " 16.·5 330 0.30 64 TABLE XVI Dielectric Strength of Phenolic Finish (Room Temperature 80°F Relative Humidity 29%) Test Micrometer Rotameter Reading D;n: Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thiclmess in Circuit recorded calculated Strength painting painting removal (A) (B) (C} (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 1.80 1.80 1.80 1. 0.176 1.53 1.38 1.53 0.15 0.15 Ool5 1 3o2 64 0.43 2. n 1.73 1.58 1.73 0.15 0.15 0.15 n 2.6 42 0.28 3. " 1.85 1.65 1.85 Oo20 0.20 0.20 ti 5.3 106 Oo53 4. n 1.85 1.68 1.85 0.17 0.17 0.17 11 4.6 92 0.54 5. " 3.10 2.90 3.10 0.20 0.20 0.20 " 13o0 260 1.30 6. " 2.13 1.63 2.13 o.so 0.50 o.so ti 14.6 290 0.58 7. 0.178 1.58 o.8s 1.60 0.73 0.75 0.74 " 14.4 285 0.39 8. n 2.10 1.28 2ol3 Oo82 o.85 0.84 ti 37.4 750 Oo89· 9. n 1.48 0.95 1.50 Oo53 0.55 0.54 " 18.4 370 0.68 10. tt 2.00 1.50 2.00 0.50 ·0.50 0.50 ti 41.6 830 1.66 11. 0.175 2.35 1.88 2.35 0.47 0.47 0.47 " 13.8 275 Oo53 12. 0.177 2.10 1.28 2.13 0.82 0.85 0.84 ti 21.8 435 0.52 13. " 2.73 1.75 2.75 0.98 LOO 0.99 ti 10.4 210 0.21 14. " 2.03 1.45 2.05 0.58 0.60 0.59 " 22.6 450 0.76 15. n 2.68 2.25 2.70 0.43 0.45 Oo44 " 7.5 150 0.34 16. 0.175 2.08 1.60 2.08 0.48 0.48 0.48 " 4.6 92 0.19 17. 0.176 2.25 1.50 2.25 0.75 0.75 0.75 " 6.4 128 0.17 18. " 3.00 2.15 3.00 0.85 0.85 0.85 " 11.2 225 0.27 19. 0.177 2.25 1.63 2.25 0.62 0.62 0.62 " 12.5 250 ·o.4o 20. ti 1~75 1.50 1.75 · · 0.25 0.25 0.25 " 30.4 610 ·. 2.44 21. 0.175 1.60 1.10 1.63 0.50 0.53 0.52 ft 7.5 150 0.29 22. .. 1.85 1.30 1.87 0.55 Oo57 0.56 s.o 100 Ool8 23. n 2.25 1.55 2.28 0.70 0.73 Oo72 "ti 7.4 150 0.21 24. 0.177 1.65 1.20 1.65 0.45 0.45 0.45 " 24.8 495 1.10 25. " 2.40 2.00 2.43 0.40 0.43 0.42 tr 30.5 610 1.45 65 TABLE XVII Comparison of Results of F.inishes Table Type of Coa tirig No. Correlation Equation of the Variance About No. of Coefficient Regression Line Regression Line Tests r volts XI vinyl 43 0.77 y = 4100x - 100 1300 XII chlorinated rubber 15 0.95 y =1600x - 130 210 XIII epoxy ester 24 0.75 y = 2200x - so 790 XIV alkyd 22 0.77 y = 470x - 60 210 xv oil 25 0.85 y= 540x - 70 220 XVI phenolic 21 0.49 y= 340x - 50 330 66 5000 I I 0 / / I I 4000 1 . . 0 / I O o0° I / / I . />o . I / I / I I ~ I 0 ~ ;:o· ~ 0 I I > / I 3000 0 I .. /o / ~ I 0 10 I ~ 0 i .....l 0 ;· 0 /. 0 I > 0 0 ~ I 0 0 g 0 I 2000 . 0 0 !c:, 0 0 I I ·lg I . / / I / I 1000 / 8 I I 1,,0 I , Q / Ao I / / I 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM TlllCKNESS, MILS FIGURE 23. BREAKDONN VOLTAGE VERSUS AVERAGE FIW THICKNFSS: VINYL FINISH. 67 ·--i-----~- ·'l 5000 4000 -1 I 1000 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 vmmm 24. BREAKDOtJN VOLTAGE VERSUS AVERAGE Filli THICKNESS: CHLORINATED RUBBER FINISH. 68 5000 4000 3000 / o/ / 2000 / / / .,. / / 0 / / / / / / / 1000 / 0 8 ;' / / / / / / / / . I 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Filli THICKNESS, MILS FIGURE 25. BREAKDOON VOLTAGE VERSUS AVERAGE FIW THICifflESS: EPOXY FSTER VINISH. 69 5000 Cf.) ~ g~ 3000 9\ ~ ~ ~ ~ 2000 ICQ 1000 -- . __ -· ·a o- - J'.' _____.. ---- - o -- ~~-o---~ _ ~~ -- · 0 --a----&' 0 Cf _() - -- -. __. . ·- - · - ~ -- ____.----o,,-::{"")1cr 0 . _ - -- 0 0 ----- 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Filli THiaCNESS, HILS FIGURE 26. BREAKDOl:JM VOLTAGE VERSUS AVERAGE FI:W THICKNESS: AUcrD l!IlllSH. . 70 5000 4000 fJl ~ 0 > .. 3000 ~ ~ ~ 0 > I ~ 2000 ~ Ico 1000 0 0 0.2 0.4 0.6 o.a 1.0 1.2 1.4 FIU.1 THICIDmSS, MILS FIGURE 27. mmAKDOclN VOLTAGE VERSUS AVERAGE Fim TlllCKNFSS: OIL FINISH. 71 5000 4000 rJ) ~ 0 > .. 3000 r:z;1 c, ~ g~ ~ 2000 ICl:l 1000 o______------. ------o 0 -- --:- 0 ------0 0.2 0.4 0.8 1.0 1.2 1.4 FIIM THICKNESS, MILS FIGURE 28 •. BREAKDOl1N VOLTAGE ~RSUS AYERAGE FILM THICKNESS: PHENOLIC FINISH. 72 5000 4000 Vinyl Cll ~ 0 > 3000 ~ ~ ~ ~ 0 > ~ 0 Epoxy Ester 2000 i Chlorinated Rubber 1000 Oil Alkyd . Phenolic 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Fim THICKMESS, llILS FIGUBE 29. OOHPARISON W BREAKDOON VOLTAGE VERSUS AVERAGE FI.Il1 THICirnESS FOR THE VARIOUS rnrrs~. 73 TABLE XVIII Dielectric Strength of Vebi cle of Vinyl Primer (Room Temperature 76°F Relative Humidity 31%) Test Micrometer Rotamet~r Rt1djn1 D£t Fjl1 Thickness Average Resistance Breakdo111 Volta&e Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) . (B) (C) (A-B) (C-B) . inches mils mils mils mils mils mils m.ecofflM mv/2 volts kv/mil reference point 0.178 1.68 1.68 1.68 1. 0.177 1.88 1.55 1.88 0.33 0.33 0.33 4 17.6 1400 4.25 2. n 1.70 1.43 1.70 0.21 0.27 0.27 " 13.0 1040 3.85 3. " 1.93 1.55 1.90 0.38 O.J5 0.37 " 15.2 1220 3.30 4. " 2.25 1.60 2.30 0.65 0.70 0.68 " 38.2 3060 4.50 5. " 2.63 1.88 2.63 0.75 0.75 0.75 tt 44.4 3550 4.73 6. 2.65 2.18 2.65 0.47 0.47 0.47 n 23.6 1890 4.02 7. " 2.15 1.78 2.15 0.37 0.37 0.37 23.4 1875 5.07 8. " 2.45 1.80 2.45 0.65 0.65 0.65 " 32.2 2580 3.97 9. "n 2.35 1.75 2.35 0.60 0.60 0.60 "It 36.4 2910 4.85 10. n 2.35 1.85 2.33 o.so 0.48 0.49 " 24.2 1940 3.96 ll. n 2.98 2.48 2.98 o• .so o.so 0.50 n 25.6 2050 4.10 12. 2.73 2.30 2.70 0.43 0.40 0.42 13.2 1050 2.50 13. " 2.55 2.05 2.55 0.50 o.so 0.50 " 18.0 1440 2.88 14. " 2.55· 2.00 2.55 0.55 0.55 0.55 n" 20.2 1620 . 2.·95 "ti 15. 2.73 2.25 2.10 0.48 0.45 0.47 " 19.0 1520 3.23 16. 0.178 1.88 1.55 1.88 0.33 0.33 0.33 16.2 1300 3.94 17. n 1.78 1.43 1.78 0.35 0.35 0.35 n" 18.4 1470 4.20 18. " 1.98 1.60 2.00 0.38 0.40 0.39 It 21.4 1710 4.38 19. " 1.83 1.55 1.83 0.28 0.28 0.28 n ll.O 880 3.14 20. " 2.40 2.10 2.40 0.30 0.30 0.30 ft 20.2 1620 5.40 21. tt 1.30 1.15 1.30 o.15 0.15 0.15 6.0 480 3.20 22. n 1.23 l.03 1.23 0.20 0.20 0.20 "It 9.8· 785 3.92 23. fl 1.56 1.33 1.58 0.23 0.25 0.24 n ll.4 910 3.79 24. n 2.08 l.73 2.08 0.35 0.35 0.35 It 20.5 1640 4.68 25. 0.179 1.65 1.35 1.65 0.30 0.30 0.30 " 12.6 1010 3.77 74 TABLE XIX Dielectric Strength of Vehicle of Chlorinated Rubber Primer (Room.Temperature 76°F Relative Humidity 25%) Test Micrometer Rotameter Readjng D!J: Filni Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal . (A) (B) (C) (A-B) (C-B) inches mils mils m:i.is mils mils mils m~gohms mv/2 volts kv/mil reference point 0.177 2.35 2.35 2.35 1. 0.175 2.10 1.93 2.10 0.17 0.17 0.17 2 9.4 375 2.20 2. n 1.95 1.75 1.95 0.20 0.20 0.20 9.8 390 1.95 3. n 2.05 1.85 2.05 0.20 0.20 0.20 n" 11.0 440 2.20 4. n 2.10 1.95 2.08 0.15 0.13 0.14 n 8.0 320 2.28 5. " 1.90 1.70 1.90 0.20 0.20 Oo20 " o.o 6. n 2.28 2.05 2.28 0.23 0.23 0.23 " ll.8 470 2.04 7. n 2.28 2.05 2.28 0.23 0.23 0.23 " 17.l 685 2.98 8. " 2.68 2.43 2.68 0.25 0.25 0.25 fl 8.3 330 1.32 9. " 2.58 2.23 2.58 0.35 0.35 0.35 " 12.2 485 l.39 lOo " 2.50 2.20 2.so 0.30 0.30 0.30 ti 13.0 520 1.73 ll. 0.176 2.95 2.30 2.93 0.65 0.63 0.64 ti 42.5 1700 2.65 12. n 2.48 1.98 2.48 0.50 0.50 0.50 " 13.8 550 1.10 13. " 2.83 2.38 2.83 0.45 0.45 0.45 " 32.6 1330 2.96 14. ti 2.7.3 2.20 2.75 0.53 0.55 0.54 " 37.8 1510 2.·so 15. ti 2.43 1.93 2.43 0.50 0.50 0.50 " 35.8 1430 2.86 16. 2.03 1.60 2.03 0.43 0.43 0.43 18.3 730 1.70 17. " 2.15 1.60 2.15 0.55 0.55 0.55 " 39.2 1570 2.85 18. " 2.10 1.73 2.10 0.37 0.37 0.37 " 20.0 800 2.16 19. "n 2.13 1.68 2.13 0.45 0.45 0.45 "ti 31.9 1275 2.83 20. " 2.20 1.50 2.20 0.70 0.70 0.70 n 28.1 ll25 1.61 21. 2.23 1.63 2.23 0.60 0.60 0.60 so.o 2000 3.33 22. "n 1.68 1.30 l.68 0.38 0.38 0.38 " 18.0 720 1.90 23. 1.78 1.35 1.80 0.43 0.45 0.44 " 35.6 1425 3.24 24. "n 1.98 1.45 1.98 0.53 0.53 0.53 "n 43.6 1745 3.29 25. n 1.98 1.45 1.98 0.53 0.53 0.53 n 25.0 1000 1.89 75 TABLE XX Dielectric Strength of Vehicle of Epo.x;y Ester Primer (Room Temperature 77°F Relative Humidity 29%) Test Micrometer Rotameter Readine: D!:t Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils· mils megohms mv/2 volts kv/mil reference point 0.177 2.18 2.18 2.18 1. 0.174 1.75 1.35 1.78 0.40 0.43 0.42 3 17.0 1020 2.43 2. n 2.48 2.45 2.so 0.03 0.05 0.04 " o.o 3. " 2.43 2.35 2.45 0.08 0.10 0.09 " o.o 4. " 2.73 2.35 2.75 0.38 0~40 0.39 n 16.2 970 2.49 5. 0.175 2.33 1.88 2.33 0.45 0.45 0.45 " 20.8 1250 2.78 6. 0.174 2.05 1.65 2.08 0.40 0.43 0.42 16.5 990 2.36 7. n 2.70 2.65 2.70 0.05 0.05 o.os "n o.o 8. n 3.00 2.70 3.00 0.30 0.30 0.30 11.0 660 2.20 9. 0.175 2.30 1.95 2.30 0.35 0.35 0.35 " 16.8 1010 2.89 10. n 2.93 2.53 2.93 0.40 0.40 0.40 "n 19.0 1140 2.85 ll. n 2.30 2.00 2.30 0.30 0.30 0.30 n o.o 12. " 2.98 2.55 3.00 0.43 0.45 0.44 It 15.8 950 2.16 13. 0.176 2.28 2.25 2.28 0.03 0.03 0.03 It o.o 14. " 2.35 2.30 2.35 0.05 o.os 0.05 n o.o 15. 0.177 2.08 1.70 2.08 0.38 0.38 0.38 tt 17.5 1050 2.76 16. 0.175 1.93 1.50 1.95 0.43 0.45 0.44 18.2 1090 2.48 17. n 2.53 2.03 2.53 o.so 0.50 0.50 "n 21.4 1280 2.56 18. 2.78 2.23 2.78 0.55 0.55 0.55 It 25.3 1520 2.76 19. "n 2.75 2.30 2.73 0.45 0.43 0.44 n 19.4 1165 2.65 20. 0.176 2.48 1.95 2.48 0.53 0.53 0.53 " 20.5 1230 2.32 21. 0.175 1.83 1.60 1.83 0.23 0.23 0.23 ti 8.2 492 2.14 22. " 2.23 1.83 2.23 0.40 0.40 0.40 n 16.0 960 2.40 23. n 2.13 1.48 2.13 0.65 0.65 0.65 tt 27.0 1620 2.49 24. n 2.48 2.35 2.48 0.13 0.13 o.13 n 4.4 265 2.03 25. n 2.75 2.75 2.78 o.oo 0.03 0.02 It o.o TABLE XXI · 76 Dielectric Strength of Vehicle of Alkyd Primer (Room Temperature 75°F Relative Humidity 25%) Test Micrometer Rotameter Readine: D!i Film Thickness Average Resistance BreakdotiD. Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A~B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.00 2.00 2.00 1. 0.176 1.75 1.35 1.78 0.40 0.43 0.42 2 44.4 1780 4.24 2. 2.00 1.58 2.00 0.42 0.42 0.42 41.2 1650 3.93 3. "n 2.00 1.63 2.00 0.37 0.37 0.37 " 34.6 1380 3.73 4. It 2.00 1.63 2.03 0.37 0.40 0.39 II" 26.2 1050 2.69 5. 0.177 2.35 1.95 2.35 0.40 0.40 0.40 " 49.4 1980 4.95 6. 0.176 2.28 1.78 2.28 0.50 o.so 0.50 II 7. 0.178 1.80 1.15 l.80 0.65 0.65 0.65 ~ ** II ** 8. " 2.25 1.58 2.25 0.67 0.67 0.67 ** 9. 1.65 1.20 1.68 0.45 0.48 0.47 ** 10. II" 2.10 1.73 2.10 0.37 0.37 0.37 "n 33.6 1340 3.62 ll. 0.176 1.50 1.05 1.50 0.45 0.45 0.45 12. 0.177 2.25 1.65 2.25 0.60 0.60 0.60 "ti ** 13. n 2.83 2.23 2.83 0.60 0.60 0.60 tt ** 14. tt 2.15 1.70 2.15 0.45 0.45 0.45 II 48.4** 1940 4.30 15. n 2.83 2.53 2.85 0.30 0.32 0.31 II 14.0 560 1.80 16. 0.175 2.20 1.80 2.20 Oo40 0.40 0.40 tt 38.0 -1520 3.80 17. 0.176 2.43 1.85 2.45 0.58 0.60 0.59 tt 18. 0.177 2.15 1~60 2.18 o.55 0.58 0.57 n 38.0** 1520 2.67 19. 2.50 2.05 2.53 0.45 0.48 0.47 37.5 1500 · 3.19 20. II" 1.90 1.80 1.90 0.10 0.10 . 0.10 n" 17.8 710 7.10 21.. 0.175 1.70 1.45 1.70 0.25 0.25 0.25 ti 22.6 900 3.60 22. 1.95 1.65 1.95 0.30 0.30 0.30 8.6 340 1.14 23. "ti 2.35 1.95 2.35 0.40 0.40 0.40 "II 32.6 1300 3.25 24 •. 0.177 1.88 1.53 1.88 0.35 0.35 0.35 It 25. n 2.50 2.38 2.50 0.12 0.12 0.12 ti 13.l** ~25 4.37 ** - no breakdo,m occurred TABLE XXII 77 Dielectric Strength of Vehicle of Oil Primer (Room Temperature 75°F Relative Humidity 24%) Test Micrometer Rotameter Reading Drf Film Thickness Average aesistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength . painting painting removal (A) (B) (C) {A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.176 2.65 2.65 2.65 1. 0.174 2.58 2.25 2.s8 0.33 0.33 0.33 2 19.5 780 2.37 2. " 2.43 2.08 2.43 0.35 0.35 0.35 n 21.4 855 2.44 3. " 2.53 2.20 2.50 0.33 0.30 0.32 " 29.8 1190 3.72 4. " 2.65 2.35 2.63 0.30 0.28 0.29 11 28.8 1150 3.96" 5. " 2.38 2.05 2.38 0.33 .0.33 0.33 " 17.6 705 2.14 6. 2.75 2.38 2.75 0.37 0.37 0.37 n 38.6 1550 4.18 7. "n 2.75 2.30 2.75 0.45 0.45 0.45 n 28.9 1150 2.56 8. 0.175 2.08 1.65 2.05 0.43 0.40 0.42 " 26.6 1050 2.50 9. o.174 3.00 2.53 3.00 0.47 0.47 0.47 It 33.0 1320 2.81 10. n 2.95 2.48 2.93 0.47 0.45 0.46 n 33.3 1330 2.89 11. 0.176 2.15 1.48 2.15 0.67 0.67 0.67 n 48.0 1920 2.86 12. 1.80 1.18 1.80 0.62 0.62 0.62 " 34.4 1380 2.22 l3o n" 2.20 1.55 2.20 0.65 0.65 0.65 14. n 2.00 1.40 2.03 0.60 0.63 0.62 "u ** 15. n 1.75 1.15 1.75 0.60 0.60 0.60 n 31.2** 1250 2.00 16. ti l.40 0.85 1.40 0.55 0.55 0.55 n 39.2 1570 2.85 17. n l.43 0.90 1.43 0.53 0.53 0.53 " 44.8 1790 3.38 18. n 1.50 1.00 1.50 0.50 0.50 0.50 ti ** 19. n 1.50 1.00 1.50 0.50 0.50 0.50 " 48.0 1920 3.84 20. " 1.30 0.83 1.30 0.47 0.47 0.47 " 46.7 1870 3.98 21. 1.50 0.88 1.50 0.62 0.62 0.62 n 45.6 1830 2.95 " fl 22. rt 1.10 0.55 1.10 0.55 0.55 0.55 ** 23. " 1.13 0.63 1.13 0.50 0.50 0.50 " 24.0 960 1.92 24. n 1.33 0.73 1.33 0.60 0.60 0.60 " 25. rt 1.35 0.70 1.35 0.65 0.65 0.65 n ** ** - no breakdown occurred TABLE XXIII 78 Dielectric Strength of Vehicle of Phenolic Primer (Room Temperature 75°F Relative Humidity 24%) Test Micrometer Rotameter Reading Dn: Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting rem.oval (A) (B) (C) (A-B) (C-B) inches mils mils mils mi.ls mils mils megohms mv/2 volts kv/ntil reference point 0.178 1.90 1.90 1.90 1. 0.176 2.70 2.45 2.73 0.25 0.28 0.27 1 36.5 730 2.70 2. 2.85 2.75 2.88 0.10 Ool3 0.12 32.2 645 5.37 3. " 2.95 2.80 2.98 0.15 0.18 0.17 "n 18.0 360 2.12 4. "n 3.00 2.75 3.03 0.25 0.28 0.27 n so.o 1000 3.70 s. 0.178 2.23 2.00 2.23 0.23 0.23 0.23 n 45.6 915 3.98 6. 0.177 2.20 1.75 2.25 0.45 o.so 0.48 2 30.8 . 1230 2.56 7. 0.178 2.70 2ol0 2.70 0.60 0.60 Oo60 n 1~ri" 8. 0.179 2.10 1.58 2.10 0.52 0.52 0.52 42.4 1700 3.27 9. n 1.55 1.18 1.55 0.37 0.37 0.37 "n 44.4 1780 4.80 10. " 2.00 1.70 2.00 0.30 0.30 0.30 " 41.6 1660 5.53 11. 0.177 1.45 1.10 1.48 0.35 Oo38 0.37 n 47.5 1900 s.13 12. 0.178 2.15 1.60 2.15 0.55 Oo55 0.55 " {~~ 13. " 2.70 2.18 2.70 0.52 0.52 0.52 n 30.2 1210 2.33 14. " 2.00 1.70 2.00 0.30 0.30 0.30 n 34.0 1360 4.53 15. " 2.73 2.so· 2.73 0.23 0.23 0.23 n . 16.5 660 2.87 16. 0.176 2.13 1.85 2.15 0.25 0.27 0.26 " 20.4 815 3.14 17. 0.177 2.30 1.83 2.30 0.47 0.47 Oo47 n 49.6 1980 4.21 18. 0.178 2.08 1.58 2.08 o.so o.so o.so " 34.4 1370 2.74 19. tt 2.35 2.03 2.35 0.32 0.32 0.32 n 16.4 650 2.03 20. n 1.80 1.75 1.80 o.os o.os 0.05 " o.o 21. 0.176 1.60 1.45 1.63 0.15 0.18 0.17 1 27o5 550 3.24 22. 1.80 1.65 1.80 0.15 0.15 0.15 n 16.3 326 2.17 23. "n 2.20 1.95 2.20 0.25 0.25 0.25 n 47.8 960 3.84 24. 0.178 1.78 1.50 1.80 0.28 0.30 0.29 n 4906 995 3.43 25. " 2.43 2 •.30 2.43 0.13 0.13 0.13 " 20.s 410 3.16 1H} - no breakdown occurred 79 TABLE XXIV ComE!rison of Results of Primer Vehicles Table Type of Coa t:ing No. Correlation Equation of the Variance About No. of C,oefficient Regression Line Regression Line Tests r volts XVIII vinyl 25 0.89 y =··4400x - 170 730 XIX chlorinated rubber 24 0.81 y = 2700x - 120 660 xx epoxy ester 18 0.99 y = 2700x - 80 100 XXI alkyd 15 0.73 y = 3600x - 60 780 XXII oil 19 0.65 y : 2200x - 320 650 XXIII phenolic 22 0.76 y = 3000x - 30 720 80 5000 4000 I I O Cl.) I I ~ I 0 I > 3000- 0 I 9' r.:i.:l I ~ I i I ~ I 0 ~ I I / ~ I I I 2000 I I ;O I Ic::Q I 0 Io o ol I Oo/ I I 1000 I I c/ o I I I I I I I 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKNESS, MILS FIGURE 30. BRFAKDOh'N VOLTAGE VERSUS AVERAGE FIIM THICKNESS: VEHICLE OF VINYL PRIMER. 81 5000 4000 / / / 2000 1000 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKNESS~ MILS VIGURE 31. BREAJillOWN VOLTAGE VERSUS AVERAGE Filli THICKNESS: VEHICLE OF CHLORINATED RUBBER PRIMER. . 5000 4000 (I} ~ ~ e\ 3000 r:::l ~H ~ ~ O· I 2000 1000 O t-L..--L-~..1..-~~-'-~~-L-~~_._~~---~~__._~~---~~ 0 0.2 0.4 0.6 0.8 1.0. i.2. 1.4 FIIM THICKNESS, MILS FIGURE 32. BREAKD01ftl VOLTAGE VERSUS AVERAGE ·Fill! THICKtmSS: .. VEHICLE OF EPOXY F3TER PRIMER. 5000 4000 {/.) ;3 . O· > 3000 I / I I / I 2000 . 0 0 I / / 0 I I / 0 / / · / / I / 1000 I 0 / 0 I I 0 / / o/,I / o/ / ,II 0 0 0.2 0.4 0.6 0.8 l.O 1.2 1.4 FILM THIClCNESS, MILS FIGURE 33. BRFAKDOWN VOLTAGE VERSUS AVERAGE FILM -THICKNESS: . 'VEHICLE OF AIJ\'YD PRIMER. ,- 84.. . 5000 4000 U) E,-4 .-4 0 > 91, 3000 t:a ~ - ~ g / ~ / 0 / ~ / / 2000 ,. 0 0 ~ /0 /. c::3 ,,. 0 0 / ,,. / 0 / / 0 ,, / / 0 0 / / 00 ~ ,,. / 1000 /0 0 ., 0 . ,, / . 8 / / ,,. / / 0 0 0.2 0.4 0.6 0~8 1.0 t.2 1.4 FIU1 Tlll~, MILS FIGURE 34. BREAKDOWN VOLTAGE VERSUS .AVERAGE -Filli THICKNESS: ·. VEHICLE OF OIL PRIMER. .. .85 . 5000 4000 ; 0 > 3000 / / I 2000 / / / / - 0 0 / 00 / / / 1000 / / / / / / / / / / 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM .THICKNESS, MILS · FIGURE 35. BREAKDOWN VOLTAGE. VERSUS AVERAGE. FILM.. TlllCKNESS: VEHICLE OF PHENOLIC PRDmR. 86 5000 Vinyl 4000 rll ;j 0 > Phenolic 3000 ~ ~ Epoxy Ester ~ ~ +-Chlorinated g Rubber ~Oil ~ I 2000 1000 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Filli THICKNESS, MILS FIGURE 36. COMPARISON OF B.REAKDOlffl VOLTAGE VERSOS AVERAGE FILM THICKNESS FOR THE VARIOUS PitruER VEHICLES. 87 TABLE XXV Dielectric Strength of Vehicle of Vinyl Finish (Room Temperature· 76°F Relative Humidity 31%) Test Micrometer Rotameter ·Reading D£r Film Thickness Average Resistance Breakdown Voltage Dielectric No. Setting before after .!after paint Thickness in Circuit recorded calculated · Strength painting painting removal (A) (B) (C)- (A-B) (C-B) . _;,,.__ inches mils mils mils .mils mils mils megohms mv/2 volts kv/mil reference point 0.180 2.28 2.28· 2.28 1. 0.178 1.95 1.85 1.95 0.10 0.10 0.10 3 5~8 350 3.50 2. n 2.12 l.85 2.12 0.27 0.27 0.27 n 16.5 990 3.67 3. It 2.25 2.05 2.25 0.20 0.20 0.20 9.6 570 2.85 4. n 2.93 2.60 2.95 0.33 0.35 0.34 "n 26.8 1610 4.74 5. 0.179 2.35 2.05 2.35 0.30 0.30 0.30 n 19.·6 1175 3.90 6. " · 2.65 2.08 2.65 0.57 0.57 0.57 " 46.0 27.60 4.85 7. " 2.85 2.28 2.-85 0.57 0.57 0.57 n 10.0 600 1.05 8. 0.181 1.50 0.93 1.53 0.58 0.60 0.59 " 30.8 1850 3.24 9. " 2.03 1.43 2.03 0.60 0.60 0.60 ".. 29.4 1770 2.95 10. " 2.55 ·2.00 2.53 0.55 0.53 0.54 u 49.6 2970 5.50 11. 0~179 2.18 1.65 2.18 0.53 0.53 Oo53 tt 49.6 2970 5.60 n 1.83· n 12. 2.33 .. 2.33 0.50 o.so 0.50 33.0 1980 3.96 13. " 2.88 2.35 · 2.85 0.53 0.50 Oo52 n 14. 0.181 l.95 1.30 1.93 0.65 0.63 0.64 n 49.6** - 2970 4.64 15. " l.68 1.15 1.68 . · 0.53 0.53 0.53 n 41.5 2490 4.70. 16. o.178 2.00 1-.60 2.00 0.40 0.40 Oo40 ft 22.0 1320 3.30 17. n 2.10 1.55· 2.1s 0.55 0.60 0.58 48.0 2880 4.96 18. tt 2.20 1.90 2.20 0.30 0.30 0.30 "n 20.0 1200 4.00 19. " 2.76 2.53 2.78 0.23 0.25 Oo24 II 15.6 930 3.88 :.20. 0.179 2.18 1.88 2.21 . 0.30 0.33 0.32 II 17.8 1070 3.34 21. 0.178 0.80 0.60 0.80 0.20 0.20 0.20 n 15.2 790 3.94 22. " 1.53 1.18 1.ss 0.35 0.37 0.36 n 24.0 1440 4.00 23. " 2.10 1.75 2.10 0.35 0.35 0.35 19.8 1190 3.40 24. n 2.58 . 2.30 2.s8 0.28 0.28 0.28 n" 16.3 980 3.50 25. 0.179 2.38 2.08 2.38 0.30 0.30 0.30 " .17.1 1025 3.42 ** - no breakdown occurred 88 TABLE XXVI Dielectric Strength of Vehicle of Chlorinated Rubber Finish (Room Temperature 76°F Relative Humidity 25%) Test Micrometer Rotameter Rea.ding D£I Film Thiclmess . Average Resistance BreakdoliD. Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.18 2.18 2.18 1. 0.175 1.88 1.65 1.90 0.23 0.25 0.24 2 o.o 2. tt 2.43 2.15 2.43 0.28 0.28 Oo28 14.0 560 2.00 3. n 2.73 2.40 2.75 0.33 0.35 0.34 " 26.2 1050 3.09 4. n 2.10 1.65 2.10 0.45 0.45 0.45 "n 23.0 920 2.04 5. 0.178 2.28 l.75 2.28 0.53 0.53 0.53 4 36.8 1470 2.78 . 6. 0.175 1.75 1.48 1.75 0.27 0.27 0.27 2 o.o - 7. 0.176 2.55 2.15 2.55 0.40 0.40 0.40 n 22.6 905 2.26 8·. n 2.83 2.40 2.83 0.43 0.43 0.43 ft 15.S 620 1.44 9. 2.65 2.20 2.68 0.45 0.48 0.47 19.2 770 1.64 10. 0.177" 2.30 2.00 2.30 0.30 0.30 0.30 "II 15.5 620 2.06 11. 0.175 2.08 1.95 2.10 0.13 0.15 0.14 n 8.0 320 2.28 12. 0.176 2.45 2.10 2.45 0.35 0.35 0.35 tt 30.8 1230 3.52 13. 0.177 2.15 1.68 2.15 0.47 0.47 0.47 ft 33.8 1350 2.87 14. " 0.95 0.70 0.95 0.25 0.25 0.25 " 8.2 330 1.32 15. n 1.55 1.45 1.58 0.10 0.13 0.12 " o.o 16. o.175 2.03 1.75 2.03 0.28 0.28 0.28 12.5 500 1.79 17. n 2.so 2.20 2.50 0.30 0.30 0.30 "11 11.0 440 1.47 18. 2.83 2.65 2.85 0.18 0.20 0.19 n 9.8 390 2.os 19. "n 2.95 2.30 2.95 0.65 0.65 0.65 n 43.4 1735 2.67 .20. 0.177 1.98 1.78 1.98 0.20 0.20 0.20 " 8.6 340 1.70 21. 0.175 1.83 1.50 1.83 0.33 0.33 0.33 n o.o 22. 1.95 1.60 1.93 0.35 0.33 0.34 It 29.4 1175 3.46 23. "n 2.00 1.75 2.00 0.25 0.25 0.25 It 15.2 610 2.44 24. n 1.53 1.33 1.53 0.20 0.20 0.20 1t 14.2 570 2.85 25. " 2.as 2.63 2.85 0.20 0.22 0.21 n o.o TABLE XXVII .89 Dielectric Strength of Vehicle of Epoxy Ester Finish (Room Temper~ture 78°F Relative Humidity 27%) Test Micrometer Rotameter Reading D£I Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Setting before ·after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A} (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.177 2.65 2.65 2.65 1. 0.176 2.40 2.00 2.43 0.40 0.43 0.42 3 14.0 840 2.00 2. n 2.60 2.33 2.63 0.27 0.30 0.29 n 15.8 950 3.27 3. 2.68 2.35 2.70 0.33 0.35 0.34 n 7.4 445 1.31 4. " 2.65 2.28 2.68 0.37 0.40 0.39 tt 19.4 1165 2.99 5. 0.177" 2.95 2.55 2.95 0.40 0.40 0.40 n 15.2 910 2.28 6. n 1.90 1.25 1.90 0.65 0.65 0.65 15.2 910 1.40 7. 0.178 2.43 1.58 2.45 0.85 0.87 0.86 "n 38.7 2320 2.70 8. 2.85 2.00 2.87 0.85 0.87 0.86 n 32.8 1970 2.29 9. "tt 2.30 1.55 2.35 0.75 o.so 0.78 n 40.0 2400 3.08 10. tr 2.73 2.25 2.75 0.48 0.50 0.49 n ~ n. 0.176 2.15 1.58 2.18 0.57 0.60 0.59 tr 22.5 1350 2.29 12. 0.178 1.90 1.08 1.88 0.82 o.so 0.81 n 26.6 1595 1.97 13. 2.45 1.58 2.45 0.87 0.87 0.87 n 38.7 2320 2.67 14. " 1.73 1.10 1.73 0.63 0.63 0.63 n 20.3 1220 1.94 15. "n 2.48 2.05 2.45 0.43 0.40 0.42 n 6.2 370 0.88 16. 0.176 1.88 1.30 1.88 0.58 0.58 0.58 n 16.0 960 1.65 17. 0.177 2.05 ;I..38 2.05 0.67 0.67 0.67 " 24.4 1465 2.19 18. 2.83 2.03 2.83 0.80 o.so 0.80 n 37.l 2225 2.78 19. o.178" 2.03 1.35 2.03 0.68 0.68 0.68 n 20.4 1225 1.80 20. " 1.55 1.40 1.63 0.15 0.13 0.14 tt ** 21. 0.175 2.38 1.80 2.38 0.58 0.58 Oo58 n 22.0 1320 2.28 22. 2.63 2.15 2.60 0.48 0.45 0.47 " 10.6 635 1.35 23. "n 2.98 2.45 2.98 0.53 0.53 0.53 n 15.0 900 1.70 24. 0.177 2.60 1.75 2.58 0.85 0.83 0.84 " 33.2 1990 2.37 25. 0.178 2.15 1.83 2.13 0.32 0.30 0.31 II 14.0 840 2.10 ** no breakdown occurred 90 TABLE XXVIII Dielectric Strength of Vehicle of Alkyd Finish · . {Room Temperature 75°F Relative Humidity ·24%) Test Micrometer Rotameter Reading D~ Film. Thickness · Average Resistance ·-Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded -~lculated Strength painting painting removal {A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil reference point 0.178 · 2.25 2.25 2.25 1. 0.176 2~05 L60 2~05 0~45 0~45 0~45 3 24~7 1480 3~29 2~ n 2~03 L58 2:00 0~45 0~42 o:44 II 20:8 1250 2~84 3~ 2~25 1:80 2~25 0~45 0~45 0~45 20~6 1240 2:75 · "n " 4~ 2~75 2:40 2:15 0~35 0~35 0~35 " 19~1 1140 3~26" 5. 0.177 2.20 lo90 2.23 0.30 Oo33 0.32 " 2208 1370 4o28 6~ n 2o55 L60 2:s5 0~95 0~95 0~95 4 40~5 3240 3~41 7~ · u 2~75 1:75 2:1s 1~00 LOO 1~00 n 3~~0 3100 3~10 8~ Ool78 2~43 1~45 2~45 0~98 1:00 0~99 n 49~0 3920 3~96 9~ n 2~85 2:03 2:8s 0~82 0:82 0~"82 fl 22:7 1820 2.22 lOo Ool79 2.30 1.58 2.30 Oo?i Oo72 0.72 · " 3206 2600 . 3.61 11~ Ool77 2~13 1:25 2:13 0~88 o:88 0~88 23~8 1900 2~16 12~ n 2~28 L40 2~28 o:88 0~88 0~88 "n 29:6 2370 2~69 13: · n 2:85 1~90 2~85 0~95 0:95 0.95 n 35:6 2850 3~00 14: Ool79 1;73 0~93 L73 0~80 0~80 0~80 II 33~4 2670 3~34 150 n lo48 0.88 1.48 Oo60 Oo60 0.60 ff 31.8 2540 · 4.23 16~ 0.176 L95 L35 1:93 0~60 0~58 0~59 II 28:0 2240 3:8o· · 17~ n 1~95 1:40 1~93 0~55 0:53 0~54 n 23~5 1880 3~48 18~ 2~25 1~80 2:23 0~45 o:43 0~44 n 12:8 · 1020 2~32 " n 19~ " 2:80 2~45 2~78 · 0:35 0~33 0~34 13~7 1100 3~23 200 0.177 2.15 lo80 2.15 Oo35 Oo35 0.35 " 10.2 815 2o33 21~ Ool75 1~95 L40 1~95 0:55 0~55 0~55 3 16~8 1010 1~84 22~ n 2~50 L98 2:50 0~52 ..0~52 0~52 n 22~8 1370 2~63 23~ 0.176 2:1s 1~55 2~1~ 0~60 0:60 0~60 II 15~8 950 1~58 24~ · n 2~60 2:1s 2:60 0:45 0~45 0~45 n 28~3 . 1700 -3~78 250 Ool77 2o38 lo93 2.38 Oo45 0.45 Oo45 n 10o4 625 1.39 91 TABLE XXIX Dielectric Strength of Vehicle of Oil Finish (Room Temperature 78°F Relativ~ Humidity 27%} Test Micrometer Rotanieter Reading D[I Film Thiclmess Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded calculated Strength painting painting removal (A) (B) (C) (A-B) (C-B) inches mils mils mils mils mils mils megohms mv/2 volts kv/mil refere11ce point 0.177 2.35 2.35 2.35 1. 0.175 2.os 1.85 2.10 0.20 0.25 0.23 1 32.6 655 2.85 2. n 1.90 1.73 1.95 0.17 0.22 0.20 " o.o 3. " 2.00 1.75 2.05 0.25 Oo30 0.28 i, 35o0 700 2.so 4. " 2.18 1.85 2.23 0.33 0.38 Oo36 n 17.2 345 0.96 5. " 1.85 1.68 1.90 0.11 0.22 0.20 n 25.5 510 2.55 6. " 2.23 2.00 2.28 0.23 0.28 Oo26 " 39.6 790 3.04 7o " 2.23 1.93 2.28 Oo30 0.35 0.33 " 34 .• 2 685 2.08 8. " 2.65 2.35 2.68 0.30 0.33 0.32 2 21.2 850 2.66 9. " 2.so 2.18 2.ss 0.32 0.37 0.35 n 22.8 910 2.60 10. " 2.45 2.08 2.50 0.37 0.42 0.40 " 28.0 1120 2.80 11. 0.176 2.73 2.25 2.75 Oo48 0.50 0.49 u 20.0 800 1.63 12. 2.40 1.90 2.45 0.50 0.55 0.53 28.5. 1140 2.15 13. " 2.80 2.30 2.83 o.50 9.53 0.52 n" 29.4 1180 2.27 14. . " 2.63 2.13 2.65 0.50 · 0.52 0.51 n 28.S 1140 2.24 15. " 2.35 1.85 2.40 0.50 0.55 0.53 " 36.5 1460 2.78 160 " 2.00 1.55 2.03 0.45 0.48 0.47 n o.o . 17. " 1.95 1.58 2.00 0.37 0.42 0.40 ti 24.8 990 2.48 18. " 2.05 1.68 2.10 0.37 0.42 Oo40 " 24.0 960 2.40 19. " 2.08 1.68 2.13 0.40 0.45 0.43 n 17.0 680 1.58 20. " 1.88 1.50 1.90 0.38 0.40 Oo39 n 17.5 700 1.80 21. " 2.10 1.70 2.13 0.40 0.43 0.42 n OoO 22. " 1.65 1.30 1.70 0.35 0.40 0.38 " 12.0 480 1.26 23. " 1.70 1.33 1.75 0.37 0-.42 0.40 " 10.0 400 1.00 24. " 1.90 1.43 1.95 0.47 0.52 o.so " . 19.4 780 1.56 25. " 1.90 1.40 1.98 0.53 0.58 Oo55 n 22.a 910 1.65 92 TABLE XXX Dielectric Strength of Vehicle of Phenolic Finish (Room Temperature 76°F Relative Humidity · 28%) Test Micrometer Rotameter Reading D!:! Film Thickness · Average Resistance Breakdown Voltage Dielectric No. Setting before after after paint Thickness in Circuit recorded .calculated Strength painting painting rem.oval .(A) (B) (C) (A-B) (C-B) inches mils mils mils .mils .mils mils megohms mv/2 volts kv/mil reference point 0.177 2.55 2.55 2.55 l. 0.176 1.98 1.53 1.98 0.45 0.45 0.45 2 46.0 1840 4.09 2. n 2.ll 1.88 2.11 0.23 0.23 Oo23 tr n.o 440 1.91 3. 2.38 2.15 2.38 0.23 0.23 0.23 12.8 510 2 •.22 4. "n 2.30 1.80 2.33 o.so 0.53 0.52 "tr 33.6 1345 2.58 5. " 2.75 2.35 2.75 0.40 0.40 0~40 n 35.6 1425 3.56 6. 0.177 2.40 1.55 2.43 0.85 0.88 0.87 3 37.2 2230 2.56 7. 2.18 1.75 2.20 0.43 0.45 0.44 ti 15.6 935 2.12 8. "ti 2.75 1.80 2.75 0.95 0.95 0.95 4 49.6 3950 4.15 9. 0.178 2.43 1.40 2.45 1.03 1.05 1.04 45.0 3600 3.46 10. ti 2.23 1.45 2.25 0.78 o.so 0.79 · "3 47.0 2820 - 3.57 ll. 0.177 1.93. 1.10 1.95 0.83 0.85 0.84 tr 12. ti 2.08 1.30 . 2.08 0.78 0.78 0.78 tt 31.6** . 1890 2 •.42 . 13. n 1.95. 1.30 1.95 0.65 . 0.65 0.65 t1 26.2 1570 2.42 14. ·0.118 2.10 1.os 2.10 1.05 1.05 1.05. 4 49.6 3950 3.76 15. ti 1.93 1.15 1.93 0.78 0.78 0.78 3 42.8 2570 · 3.29 16. 0.175 2.70 2.05 2.73 0.65 0.68 0.67 n 42.6 2550. 3.80 . 17. ti 2.83 2.15 2.83 0.68 0.68 0.68 n 35.7 2140 3.14 18. 0.176 2.25 1.50 2.30 0.75 0.80 0.78 " 34.7 2080 2.67 19. 2.23 2.00 2.25 0.23 0.25 0.24 11 9.8 590 2.45 . 20. "n 2.50 2.10 2.50 0.40 0.40 0.40 tr 20.5 1230 3.07 21. 0.175 2.68 2.03 2.68 0.65 0.65 0.65 ti 38.4 2310 3.55 22. n 2.65 2.15 2.65 0.50 ··0.50 o.so n 17.4 1050 2.10 23. " 2.88 2.25 2.90 0.63 0.65 . 0.64 If 34.8 2090 3.26 24. 2.13 1.95 2.15 0.18 0.20 0.19 " 8.5 536 2.82 25. "tr 2.98 2.55 2.98 0.43 . 0.43 0.43 n 20.0 1200 2.79 **· - no breakdown occurred 93.. TABLE XXXI Comparison of Results of Finish Vehicles Table Type of Coating No. Correlation Equation of the Variance About No. of Coefficient Regression Line Regression Line Tests r volts xxv vinyl 23 0.90 y =4900x - 290 780 XX.VI chlorinated rubber 20 0.85 y = 2700x - 130 480 XXVII epoxy ester 22 0.85 y = 2700x - 280 700 XX VIII alkyd 25 0.84 y = 3200x - 130 1000 XXlX oil 22 0.58 y: l600x - 210 480 xxx phenolic 24 0.93 y = 3800x - 380 800 94 · 5000 4000 I I I I I I I 3000 o/ I I ' I I ·/ I -- /. 2000 1000 0 0 0.2 0.4 0.6 0.8 1.0 FIW THI~, MILS . FIGURE 37. BREAiffiOWN VOLTAGE VERSUS _AVERAGE FIUi TlllCKNESS: ·. · VEHICLE OF · VIlllL FINISH. 95 5000 4000 rJ) ;3 0 ~ 3000 / / / r / / / // / 0/ / / / / 0 //, ./ / 0 / / ~ ·.. · // / / CJ. / / / a· // / 1000 / ~ 0 / .,,/ / 0// // o ~8/o . /o/ / 0 / 0/80 / / / 0 / 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 - FILM THICKNESS, MILS .. FIGtmE 38. BREAlOJOlm VOLTAGE VERSUS-AVERAGE FIW: THICKNESS: VEHICLE OF CHLORINATED RUBBER FINISH. 96 5000 4000. / / / / //o d> / 0 / / / 2000 · / / / / / / / / / 0 / / / / / / / / 0 / 1000 / / / 0 0 0 0 / ., 0 / / / / 0 / / 0 / / / 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICK~, tllLS FIGURE 39·. BREAKDOttN VOLTAGE VERSUS AVERAGE Fiill THICKNESS: VEHICLE OF EPOXY ESTER FINISH. ; .·· .. , 97.' 5000 / / 4000 la / /· I / ,/ / a, / / / / / / ~ - 0 / / ·' g / o· / / 9\ 3000 / / _, / ~ I 6 ~ / 0 H 0 / g 0 / ·o / ~ / 0 I I / 2QOO / 0 / / / 0 /· / 0 / I I / 0 I / ·' / 0 / / / 0 / /0 / / 1000 · 00 / / ro / /o /. / 0 / / / / / , / 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKNESS, MIIS FIGURE 40. BREAlmoWN VOLTAGE VERSUS ~ VERAGE FILM THICiarass: VEHICLE OF ALKYD FINISH. '98 5000 4000 Cl) ~ - 0 > 3000 2000 ,.. / 1000 / • 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 FILM THICKNESS, 1llLS . FIGURE 41. BREAKDOWN VOLTAGE VERSUS AVERAGE Filli THICKNESS: VEHICLE OF OIL FINISH. ,99 5000 4000 · I 0 0 / I -1 I I . I / JI I I I t'l I / I E-4 I I ~ - I 0 > I 3000 I I "' I I ~ I i I o/ I ~ g I 0 d I - I I I o I I I I o; 8 I ol 0 I I 2000 I I ,/ ! I 0 o/ ~ I I I ·; I I I 0 I. I . I )6/o I I . 0 1000 I I I O / I I I I I 0 I I 1 I I I I 0 I 0 0.2 0.4 0~6 0.8 1.0 1.2 1.4 FIIM THICKNESS, MILS FIGURE 42. BREAK.DOWN VOLTAGE VERSUS AVERAGE FIW THICKNESS: VEHICLE OF PHENOLIC FINISH. 100 5000 Vinyl 4000 Phenolic ~ f-4 ~ · 0 > Alkyd ~ 3000 ~ ~ Chlorinated g Rubber ~ "Epoxy Ester 2000 Ir:o Oil 1000 0 0 0.2 0~4 0.6 0.8 ·1.0 1~2 1.4 FIIM THICKNESS, MILS FIGURE 43. CX>MPARISON OF BREAKDOl-JN . ~LTAGE VERSUS AVERAGE FILM THI~ FOR THE VARIOUS FINISH VEHICLES. 101 Sample Calculations Examples of the various types of calculations made in this investi gation are presented in ·this section using the data and results of Table IV . Calculation of the Dry Film Thickness. · The dry film thickness values were obtained by subtracting the values in column B from the re spective values in columns A and C. As an ~lustration, test number 1 of Table IV is used. The values for columns A, B, and C respectively are 2. 45, 1. 85, and 2. 48 mils. The values reported for the dry film thick ness are: 2. 45 mils - 1. 85 mils= 0.60 mils 2. 48 mils - 1.85 mils= 0. 63 mils Calculation of the Average Dry Film Thickness. The two values obtained for the dry film thickness were averaged and recorded as the average thickness. Conversion of Recorder Readings to Breakdown Voltages. The values of the breakdown voltage in volts were calculated by multiplying the re spective values of the recorded breakdown voltage by the appropriate con version factor, depending on the number of 1-megohm resistors in the measuring circuit. The conversion factors for 1, 2, 3, 4, and 5 resistors respectively, are 20, 40, 60, 80, and 100. They were detennined as follows: The voltage determining range of the recorder for 1, 2, 3, 4, and 5 re sistors respectively, was Oto 1000, 2000, 3000, 4000, and 5000 volts. The chart paper of the recorder was divided into 50 units for the 100 millivolt range. To avoid confusion, the recorder readings were read directly from the chart paper and recorded as millivolts/2. Therefore, the voltage range divided by 50 gave the conversion factor. The following 102. · example was taken from test number l of Table IV. The m1:}llber of 1-megohm resistors was 4 with a recorder reading of 40.0. Therefore,.the break ·down voltage in volts is 40.0 x 80 = 3200. volts Calculation of the Dielectric Strength. The values of the calculated. breakdown voltages divided by the corresponding average film thiclmess gave the dielectric strength. For instance: · 3200 volts _.5 1 6 -1 /mil 1000 X 0.62 mils e1 • {V Rejection of a Dielectric Strength Value. Since there were· some doubtful dielectric strength values, these were examined prior to further calculations, for possible rejection. The rejection of an obviously high or low value of the dielectric strength was possible by the use of the ncri'terion for Rejection qf an Observationn(35). The three steps followed are stated below. 1. The mean and average deviation from the mean ,-ra.s calculated, omitting the doubtful value. 2~ The deviation of the doubtful value from the mean was calculated. 3. If this deviation was equal to or greater than four times the average deviation found in step 1, the observation was rejected. · "According to probability theory, 99.3 per cent of. the observations . in a given series have error~ equal to, or less than four times the aver.age deviation. Hence any observation which deviates more than ( S) this has only seven chances in one thousand of being a.correct one" 3 • The following is an illustration of this procedure as applied to ·Table IV for vinyl primer. Visual observation revealed that test nwnber 20 of the dielectric streng:th was low compared to the other values. The mean and average deviation, omitting the doubtful value (3.74 kv/mil); of 103 these values were calculated and fotmd to be 4.97 and 0.22 respectively. Four times the average deviation of these values was 0.88 • .The deviation from the mean of the value in question was 1.23. Since 1.23 was greater than 0.88, test number 20 could be rejected. Calculation of the Correlation Coefficient(s). On plott~g the average film thickness against the breakdown voltage, graphs were obtained showing wide scatter in most cases, but apparently a decide4 tendency for greater film thicknesses to give higher breakdown voltage values. To test for the significance of this apparently linear relation, the correlation coefficient r was calculated using the following definition: If the relation between the pairs of observations can be represented by a straight line wi. th complete confidence, r =±1, positive if the line has a positive slope and negative if the line has a negative slope; if there is no relation between the variables, r = O. Having calculated the value for r, it can be determined whether the observed value is larger than would be obtained accidentally in the absence of a correlation. To do this, the table of r values in Appendix 4 was entered with degrees of freedom two less than the number of pairs of observations. An r value in that row, which ·was closest to the calculated value of· r,: was located. If this value, for instance, fell closest to that given for the 1 per cent level of significance, it could be said that the chances of there being a correlation were 99 in 100. For the evaluation of the correlation coefficient the information shown in Table XX.XII had to be computed. In this table, xis the average 104 TABLE XXXII Values Required for Calculation of the Correlation Coefficient of Vinyl Primer Test No. x y x2 r2 xy 5 1. 0.62 3200 0.38 102 x 10 1980 2. 0.65 3100 0.42 96 2020 3. 0.65 3510 0.42 123 2280 4. 0.67 3340 0.45 112 2240 s. 0.65 3400 0.42 116 2210 6. 0.70 · 3180 0.49 101 2230 7. 0.92 4220 0.85 178 ·3880 8. 0.95 4600 0.90 212 4370 9. 10. 0.75 3870 0.56 150 2900 11. 0.72 3890 0.52 151 2800 12. 0.72 3560 . 0.52 127 2560 13. 0.60 2830 0.36 80 1700 14. 15. 0.34 1690 0.12 29 580 16. 0.73 3870 0.53 150 2830 17. 1.00 4960 1.00 246 4960 18. 0.77 3550 0.59 126 2730 19. o.so 4080 0.64 167 3260 20.a 21. 22. 23. 0.90 4680 . 0.81 219 4210 24. 0.58 2640 0.34 70 1530 25. 0.65 3220 0.42 104· 2090 5 t 14.37 71400 10.75 2660 x 10 53400 (E_x) 2 = 206.5 2 (~y ) : 5.10 x 109 a rejected data 105 dry film thickness and y is the calculated breakdown vol-tage. ~ving ·this information, the calcula~ion of the correlation coefficient was made as follows: (ix)2 n n = the number of pairs of observations 206.5 = 10.75 - --- 20 : 0.42 {Iy)2 n 9 8 5.10 x 10 : 2.66 x 10 ------20 :: 1.09 x 107 ~(x - x){y - y) : r(x.r) - i: (x) r(y) n 4 (14.37)(7.14 x 104) : 5.34 x 10 · ------20 = 2.oa x 103 Substituting these · values in equatioi1 (1) the following calculation resulted: 2.os ·x 103 r = --======...:. V(0. _42) (l.09 x 107) r = 0.97 The above value of r is large and not listed in the table of . correlation coefficients (Appendix 4). If the significance levels · had extended sufficiently far it was estimated that the probability of these data not representing a straight line was about one chance· in a · million. 106 Calculation of. the Equation for the Regression Line(G). ~ving · established ~hat_ there 1vas a _correlation between the variables (dry film thickness and breakdo~.voltage) and that· a str~ight line was appropriate, it wa.s necessary to find the equatio_n for this relationship. The formula for finding the· most probable value ~f y ·corresponding to a given value of x ( teclmically known as the regression of y upon x) is: y = a+b(x· - x). (2) Using Table XXXII and values obtained .in the calculation of the correlation coefficient on page 105, the following values for a, .b, and x 1-rere calculated. 7.14 x 104 3 a= y = ~ = = 3.57 x 10 n . 20 3 ~(x - x)(y - y) = 2.08 x 10 b - - 4.95 x 103 l(x - x)2 0.42 _ ~ x 14.37 x = ---- = - 0.72 n 20 Inserting the above values into equation (2) the following calcu- lation resulted: 3 y = 3.57 x 103+ 4.95 i 10 (x - 0.72} y = 4950x + 10 = 5000x +·10 Calculation of the Residual Variance About the Regression Line. · If the regression line was to be used to predict values of y from known values of x, limits had to be shown between which there was a certainty as to the correctness of the prediction. In all cases confidence limits of 95 per cent were calculated in this investigation. This is to-say that ,vithin these limits, 95 per cent .?f all points would fall. 107 The standard deviation CTr .of the scatter, measured in uni:ts of y · parallel to ~he y-axis, is given by: ;t(y - y)2 c5'r = J 1 - r2 J (3) n - 2 Where: n is the number ·of pairs of observations r is the correlation coefficient Substitution in equation (3) with values obtained :in previous sections, yields: 1.09 x 107 a'r : J 1 - 0.94 ~8 The confidence limits lvere then calculated from the expression: variance = t ~ r (4) The value oft for n 2 degrees of freedom and 5 per cent level of significance (95 per cent confidence limits) was found in the table of t values in Appendix 5. Substitution into equation (4) yields: 2.10 x 191: 400 Two lines were then dra,vn, one displaced 400 tmits of y downward and one 400 units of y upward from the regression line. Thus, using the regression line to predict the value of y from a known value of x, these confidence lines gave the limits betl11een which there was a 95 per cent chance of being corre.ct in the prediction. 108 IV. DISCUSSION The discussion~~ presented in three sec~ions: (1) discussion of results, (2) recommendations, and (3) limitations. Discussion of Results Correlation Coefficients. To test for the significance of the apparently linear relation between.breakdown.voltage and the dry film thickness, correlation coefficients were calculated as shown in the sample calculations. The correlation coefficient has either a value of plus or minus l if· there is a perfect relationship between two variables or O if there is no relation at all. A value falling between these limits places determinable significance on the results. In this research the lowest value obtained for the correlation coefficients was 0.49 for phenolic primer. Following the procedure given in the sample calculations it was found that there were 98 chance~ in 100 that there was a direct relationship between the breakdown voltage and the film thickness. Correlation coefficients ··· were calculated for all films with significance .- . . .. found to be greater than that of phenol'.ic primer in all cases. Equation for the Regression Line. The method for calculation of the most probable value of y (breakdown voltage) corr~sP;onding to a given value of x (film thiclmess) is shown in the sample calculations. Expressions_ were found for each set of data. The regression line i _s not to be confused with the true relationship of the variables. It merely makes the best possible estimate of y from a known value of x, using a certain number of experimental data. Teclmically ~his line gives the squares of the deviation 109 of every point, measured parallel. to the y-axis in units- of y, sunnned for all point_s, as a ndnimum. Residual Variance About· the Regression Line. The variance was calculated for each set of data and an example is shown in the sample calculations. The 95 per cent confidence.limits that were assigned in all case·s means that 95 times out of 100, the true population will fall within these limits. The assignment of the 95 per cent confidence limits is arbitrary. Comparison of Primers. · Figures 16 through 21 show the relation ship of breakdown voltage to film thickness. Both the regression line and the variance are included. In figure 22 all primers are compared ,vi.th each other (variance omitted). The order of -decreasing dielectric strength for the various primers taken from this figure is as follows: vinyl, alkyd, chlorinated rubber, epoxy ester, oil, and phenolic. It is worthy to note that the dielectric strength of vinyl primer is t,vice as great as that of alkyd primer, the n~ highest. On the other hand, phenolic primer is the lowest in dielectric strength and only one half of that of oil primer. Comparison of Finishes. _Figures ·23 through 28 show the relation ship of breakdown voltage to film thickness. Both the regression line and the variance are included. In figure 29 all finishe~ are compared ,vi.th each other (variance omitted). The orde·r of decreasing dielectric strength for the various finishes taken from this figure is as follows: vinyl, epoxy ester, chlorinated rubber, oil, alkyd, and phenolic. Vinyl finish has nearly twice the dielectric stre:q.gth of the next highest, epoxy ester finish. Comparison of Primer Vehicles. Figures 30 through 35 show.the relationship ~f breakdown voltage to film thickness for each.of the primer vehicles. Both the regr~ssion line and the variance are shown. Figure 36 shows a comparison of all the primer vehicles with the variance omitted. The order of decreasing dielectric str.ength is as follows: vinyl:, alkyd, phenolic, chlorinated rubber, epoxy ester, and oil. The dielectric strength values and the order of decreasing dielectric strength have been greatly changed due to removal of the pigment. Comparison of Finish Vehicles. Figures 37 through 42 show the relationship of breakdown voltage to film thickness for each of the finish vehicles. Both the · regression line and variance are shown. Figure 43· shows a comparison of all the finish vehicles with.the variance omitted. The order of decreasing dielectric strength is as follows: vinyl, phenolic, alkyd, chlorinated rubber, epoxy ester, and oil. Again the di~ectric strength values and their order have greatly changed due to pigment removal. 111 Recommendations .• There are munerous ways in which this investigation could be extended and improved. ·Ea.ch recommendation ,'lill be discussed under its appropriate heading. Relay System for Power Supply Disconnection. In this_ investigation, the breakdown point was noted by a rapid reversal of direction of the recorder pen at which time the power supply was turned off manually. In some instances, it was noted that there wa.s some sparking through the coating before complete breakdown had occurred. This created confusion to the observer due to the erratic movement of the pen. An appropriate relay system placed in the measuring circuit could be employed to auto- matically turn off the power supply upon complete short circuit. Ad,iustment of Support-Arm Legs of the Thiclmess Gage. At present, the adjustment of these legs to reset the gage to the reference point rotameter reading is facilitated by the use of two hex head bolts. Since this does not allow an easily obtainable fine adjustment without considerable patience, it·is recomniended that these be replaced by two micrometer screws. Nrnnber of Tests. An increase in the number of tests from 25 to 50 on each film would allow a more accurate evaluation of. the data. Film Thickness Range. Dielectric· stre~gth test's liere not performed on films of greater thickness than 1.5 mils. An extension of this range to 3 or 4 mils.would allow better comparisons to be made. Temperature. Since, according to theory, an .increase or decrease in temperature will cause a change in the dielectric strength, it is . ' suggested that some work be done at controlled temperatures and over a· 112 range similar to that encountered in field testing • . Humi Limitations The work done in this investigation was governed by the.following limitations. Number of Tests. The number of te~ts performed on each film was fixed a~ 25 with the exception of vinyl finish for which SO.tests were used, Paints. The primers, finishes, and vehicles of the same, were supplied by Corrosion Project No. 1 of the Corrosion Committee of the Federation of Societies for Paint Technology. All were proprietary materials .. Ambient Temperature. The laboratory used ~or this inv~stigation varied in temperature from 75 to 81 0 F. Relative Humidity. The laboratory used for this investigation varied in relative humidity from 24 to 44 per cent. Transformer. The transformer used had a direct current voltage range of from Oto slightly greater than 5000. · Recording System. ·The recording. system was designed to accomodate the voltage range of the transformer. Film Thickness. Film thicknesses beyond 1.5 mils.were not used beqause of the limitation of ava?-lable voltage to break them down. Duration -of Stress. The d~ation of voltage application was in . all cases less than 20 seconds and varied-within this range with.the voltage necessary to break down the film. 114·· V. CONCLUSIONS The determination of the dielectric strength of some proprietary · anti-corrosive primers; finishes, and their vehicles. of the general types vinyl, chlorinated rupber, epoxy ester,·alkyd~ -oil, .and phenolic by means of a high voltage direct current source and a pneumatic thickness gage led to the fo:µ.o~ conclusions: 1. The dielectric s~rength, in_all cas~s, was found to be inde pendent of the film thickness in the range examined of 0.10 to 1.50 mils. 2. There are diffe ·rence's in the · dielectric .strength values for each type of paint varying· from 0.2 to 2.8 kv/mil. 3. The dielectric st~engths of the vehicles were higher than those · of the corresponding primers or finishes; increases of 10% up to tenfold were determined. A further evaluation of the results could not·be made at the present time nor was it possible to draw additional conclusions since all data of the field tests of these coatings were not available. 115 VI. SUMMA.RY Many methods for the quick evaluation of the.protective proper- . . ties of anti-corrosive paints have been attempted. No one method has given conclusive· evidence of answering the problem. As a new a.pproach, the dielectric strength was determined for some commercial anti-corrosive paints ,vhich are undergoing considerable field testing. The purpose· of this investigation was to evaluate the feasibility of employing dielectric strength determinations as a quick and ral:.atively easy method for the evaluation·of the protection that a particular coat ing would give to a· metal substrate. A pneumatic gage was designed for the accurate determination of the dried paint film thiclmesses. Overall magnification of the thickness ·was 2300 times. Reproducibility of thickness readings was found to be plus or minus 13 microinches. The paint films were broken down by controlled high· voltage direct current supplied to a sphere on plane electrode system. A circuit for the determination of the breakdown voltage .was designed. This circuit consisted of a voltage divider of I-megohm resistors in series with a recording potentiometer. The breakdown voltages were re.corded in milli volts from this recorder and converted to volts using appropriate con- version factors. Correlation coefficients were calculated for each film teste.d to place significance on the results. It was found that the relationship between breakdown voltages and dry fil.ni thicknesses ·could b.e represented by a straight line. The equation of the relationship ,ras found along · with the variance about that line. · 116 The dielectric ·strengths were compared for .the . six proprietary paint primers., finishes, and vehicles of the same. The types of paint used were: vinyl, chlorinated rubber, epoxy ester, .alkyd, oil., and phenolic. Through the comparisons it was determined that removal of the pigment to obtain the vehicle increased the dielectric str¢ngth and that there were determinable differences in the dielectric strengths obtained. Since the results of the field tests were not yet available, no further conclusions could be drawn ·as to the validity of this as a quick method for the evaluation of the protective value of these coatings. 117 VII. APPENDICES For completeness_~he following sections include a list of materials and apparatus used in the investigation, calibration data on the pneumatic thickness gage, ·and tables of correla~ion.coefficients and t values used in the statistical analysis of the results. 118 Appendix 1 ·Materials . Calcium Chloride. Purified, anhydrous, ·a-mesh, granulated, J. T. Baker Chemical Co., Phillipsburg, N. J. Used to dry air prior to entering thickness gage. Construction :Materials for Pneumatic Thickness Gage. Obtained from stockroom of the Department of Chemical Engineering of the Missouri School of Mines and :Metallurgy, Rolla, Missouri. Paint Remover. One quart can, Paint and Varnish Remover, Demert and Dougherty, St. Louis, Missouri. Used to remove paint from panels after use. 119 Appendix 2 Apparatus Air Tubing. Nekoron P, 3/16" I.D., Samual Moore and Co., 1:lantua, Ohio. Used for all air connections _on thickness gage. Baker Film Applicator. 8" gate, Oto 10 mils wet film application., Gardner Laboratories, Bethesda., Md. Used to apply wet paint film to steel panels. Ball Bearings. in steel, high polish, obtained from the .stockroom of the Department of Chemical Engineering of the :Missouri School of Mines and Metallurgy, Rolla, Missouri. Used as high voltage probe for break down voltage determinations. Banana Plug. Hex nut., spring type, No. 8994., General Cement Co • ., Rockford, Ill. Used for multiple arrangement of 1 megohm resistors. Binding Post. No. 7783-1, General Cement Co., Rockford, Ill. Used with banana plug. Condenser. Glassmike, ASG-204-Bm, 0.2 mfd, 8~ WVDC, Condenser Products, N. H., Conn. Used to remove any remaining alternating component from the high voltage.source. Dry Cells. 1-! volt, Wizard No. 3-B-6916, Western Auto Supply Co. Used to activate cathode of 1B3 voltage rectifier tubes. Gardner Mechanical Film Applicator. 9" x 12n vacuum plate surface, 110 volt, 60 cycles, application speed - in/sec., Gardner laboratories, Bethesda, Md. Used to move Balcer Film Applicator at a uniform rate while coating steel panels. Inside :Micrometer. No. 1218, Millers Falls Co. Used on thiclmess gage. 129 Masonite Board. 1/8" thick, Powell Lumber Company, Rolla, Missouri·. Used to construct template, resistance board, and circuit board. Powerstat. 110 volt, ~O cycle, 7 amp, Superior Electric Co., Bristol, Conn. Used to control input voltage to transformer. Recorder. Brown Electronik, model 153-X17V-X-30, amplifier no. 351959-J, converted to Oto 100 millivolt range, 110 volt, 60 cycle, 0.60 amps,.60 watts, serial no. 589434, Minneapolis Honeywell Company. Used to record the breakdown voltages. Resistors. I.R.C. deppsited carbon precision resistors, 1 megohm, 1 watt, 1%, DCF-1%, RN-25X, l004F, International Resistance Co., Phila., Pa. Used as voltage divider for breakdown voltage determinations. Rota.meter. Precisionaire, Ser. No. A-398,. Sheffield, Sayton, Ohio. Used to measure air flow rate for thickness gage. Socket. 8 prong, General Cement Co., Rockford, Ill. Used to mount 183 tubes and to facilitate wiring. Speed Reducer Motor. Type NSI-33R, 110 volt, 60 cycle, single phase, continuous duty, 0.010 H.P., 37.5 rpm, 30:l ratio, Bodine Electric Co., Chicago, Ill. Used ·to control application of voltage with power- stats. Steel Panels. Steel bars cold finished C-1018, l/4" x 8" x l'-0", ha~ksawed to.length and deburre~,- one side highly polished, flatness within 0.005", Joseph T. Ryerson & Sons, Inc.-, St. Louis,.Mo. Used as substrate on which paints were applied. Taylor Humidiguide. Wet-dry bulb type, non-recording, Taylor Instrument Company, Rochester, N.Y. ·Used to determine relative humidity. Transformer. Neon sign, center tap, 7500 volts, 18 milliamps, General Electric Co. Used as high.voltage power supply. 121 ~· 10,000 volt, Cathe.de ray, #20 Str • ., 441A, _Alpha Wire Corp., _ New York., N; Y. Used for all wiring in the high voltage circuit. Voltage Rectifier Cap Clip. Wadsco Elec-tronic Manufacturing Co., Los Angeles, Calif. Used to connect high voi tage lead from transfonner :fo 1B3 tubes. Voltage Rectifier Tubes. 1B3•GT, Raytheon, Westwood, Mass. Used to convert high voltage alternating current to direct current. 122 Appendix 3 Calibration of the Pneumatic Thickness Gage The thickness gage was calibrated by means of standaz:tl production gage blocks. The down-stream pressure was fixed at 30 pounds per square inch with the measuring head closed off. Using the scale that was original equipment on the rotameter, the following procedure was used. 1. A glass panel was placed on the supports tmder the measuring head of the gage and made stationary. 2. 0.1030 and 0.1010 inch gage blocks 1rere placed together beneath the measuring he~d. 3. Using the micrometer, the measuring he.ad was lowered until a readmg of 1 was obtained on the rotameter scale. This reading was recorded along with the total thickness of the two gage blocks. The micrometer was not readjusted during the remainder of the calibration. 4. Leaving the 0.1030 inch gage block and replacing the 0.1010 inch gage block with a 0.1009 inche gage block, a new rota.meter reading was obtained and recorded. 5. Leaving the 0.1030 inch gage block and replacing the 0.1009 inch gage block with a 0.1008 inch gage block, a new rotameter reading was obtained and recorded. 6. The preceding was continued, removing 0.0001 inch for each rotameter reading, until the entire scale had been scanned. 7. This process was repeated twice more and the data averaged. Figure 44 shows average old scale readings versus combined gage block thicknesses. Using this inf'ormation a new scale for the rotameter 123. was cut in plastic with O on the-new scale being set at·the same.position as l on the -~ld scale. It should be noted that the scale as made compensated for the slight curvature show in Figure 44. The cause of this slight deviation from a linear relation was assumed to be ca~sed by a slight decrease in· dow stream pressure as the perpendicular distance increased between the measuring head and the gage block surface. After the new scale was made and installed, its correctness wa.s confirmed· with the gage blocks. No errors were noted in the scale. The new scale installed m the rotameter is shown in Figure 45. No statementas to·the accuracy of the thickness mea~urements could be made since the accuracy of the thickness· standards was not kno,m. The overall magnification of the thickness was 2300 times. Reproduci'.""' bility was found to be plus or minus 13 microinches. '124· . 0.2040 ; 0.2035 0z H "'II Ct.,fa ~ 0.2030 ~ 0 ~ E-4 !:.: 0 8 ~ 0.2025 ~ £":. 0 0.2020. ------, - - ---. - 0~ E-c 0.2015 I . I 0.2010 .. l 1.5 2 2.5 3 3.5 4 4.5 5 ROTAMETER READING* (OLD SCALE), SCALE DIVISIONS I I I 0 0.5 l 1.5 . 2 2.5 3 ROTAMETER READING* · (NEW SCALE), MILS . FIGURE 44. CALIBRATION CURVE FOR PNEUMt\TIC THICKNESS GAGE. * Average of three trials· 125 Figure 45. New Scale Installed in Rotameter. 126 _Appendix 4 eo·rrelation Coefficients r level ·of significanc _e 0.10 0.05 0.02 0.01 0.001 degrees of freedom 1 0.988 .0.997 0.999 1.000 1~000 2 0.900 0.950 0.980 ' 0.990 0.999 3 0.805 -0.878 0.934 0.959 0.992 4 o. 729 . 0.811 . 0.882 0.917 0.974 5 0.669 0.754 0.833 0.874 0.951 6 0.621 0.707 0.789 0.834 0.925 7 0.582 0.666 0.750 0.798 0.898 8 0.549 0.632 0.716 0.765 0.872 9 0.521 0.602 0.685 0.735 0.847 10 0.497 0.576 0.658 0.708 0.823 11 0.476 0.553 0.634 0.684 0.801 12 0.457 0.532 0.612 0.661 0.780 13 0.441 0.514 0.592 . 0.641 0~760 . 14 0.426 0.497 0.574 · 0.623 0.742 15 0.412 0.482 0.558 0.606 0.725 16 0.400 · 0.468 0.543 o·.sgo 0.708 17 0.389 0.456 0.528 0.575 0~693 18 0.378 0.444 · 0.516 0.561 0.679 19 0.369 0.433 o.so3 0.549 0.665 20 0.360 0.423 0.492 0.537 0.652 25 0.323 Q.381~ 0.445 0.487· 0.597 30 0.296 0.349 0.409 o• .44.~ 0.554 0.275 0.325 0.381 0.418 0.519 35 ' 40 0.257 0.304 0.358 0.393 o.~90 45 0.243 0.287 0.338 0.372 0.465 Fisher, R. ,A..: "Statistical Methods for Research Workers," p. 177. Oliver and Boyd Ltd., London, 1938. 127 Appendix 5 · t values t level of significance 0.10 o.os 0.02 0.01 0.001· . degrees of freedom 1 6.31 12.71 31.82 63.66 636.62 2 . 2.92 4.30 6.97 9.93 31.60 3 2.35 ~.18 4.54 5.84 12.94 4 2.13 2.78 3.75 4.60 8.&1 5 2.02 2.57 3.37 4.03 . 6.86 6 1.94 2.45 3.14 3.71 5.96 .7 l.90 . 2.37 3.00 3.50 5.41 8 1.86 2.31 2.90 3.36 2.04 9 1.83 2.26 2.82 3.25 · 4.78 10 1.81 2.23 2.76 3.17 4.59 11 1.80 2.20 2.72 3.ll 4.44 12 1.78 2.18 2.68 3.06 4.32 13 1.77 2.16 2.65 3.01 . 4.22 14 ·l.76 2.15 2.62 2.98 4.14' 15 1.75 2.13 2.60 . ·2.95 4.07 16 1.75 2.12 2.58 2.92 4.02 17 1.74 2.ll 2.57 2.90 3.97 18 1.73 2.10 2.55 2~88 . 3.92 19 1.73 2.09 2.54 2.86 3.88 20 1.73 2.09 . 2.53 2.85 3.85 21 1.72 2.08 2.s2 2.83 3.82 22 1.72 2.01 2.51 2.82 · 3.79 23 1.71 2.01 2.50 2.81 3.77 · ·24 1.71 2·.05 2.49 2.so 3.75 25 1.71 2.06 . 2.48 2.·79 ',; 3.73 30 lo70 2o04 24!46 . 2.75 3.65 40 1.68 2.02 2.42 2.70 3.55 60 1~67 2.00 2.39 2.66 3.46 Fisher, R. A. : nstatis ti cal Methods for Research Workers," p •. 214. · Oliver and Boyd Ltd., London, 1938. 128 VIII. BIBLIOGRAPHY . 1. Austen, A. Eo W.: Dielectric Properties of Homogeneous Materials, J. Inst. Elect. Engrs., ~' 373, (1945) .• 2. ------and H. Pelzer: The Electric Strength .of Paraffins and Some High Polymers, J. Inst. Elect. Engrs., 21, part 1, · _ 525.,.(1946). 3. · B~, I. D. L.·: Intrinsic Electric Strength of Polyvinyl Alcohol and its Temperature Relation, J. Inst. Elect. Engrs., 98, part 1., 84., (1951). · 4·. Berberich, L. J., and R. Friedman: Stabilization of Chlorinated Biphenyl in Paper Capacitors, ·Ind. Eng. Chem., 1:2., .. 117., (1948). 5. Brownlee, K. A.: "Industrial Experimentation"~ p. 62. Chemical Publishing Co., Inc., New York, 1949. 6. ibid, p. 63. 7 •. ibid, p. 65. a. Da~s, R. J.: High Voltage Research at. the National Physical Lab oratory, J. Inst. Elect. En.grs., 93, part 1, 177, (1946) • . 9. Evans, J. C.: The Pne_umati? Gauging Technique in its Application to Dimensional Measurement,. J. Inst. Prod. Eng., .J.§.,'. no, (1957). 10. · ------' M. Graneek, and· H. G. Loe: Continuous ·Pneumatic Gauging of Material in Thread or Wire ~orm, Trans. Soc. Instrwn. Tech' • ., ,. ~' 34, (1950). 11. ·, and I. G. Morgan: A Pneumatic Apparatus for Measuri:ng the Flatness of Photographic Plates, Engineering, 180, 510, (1955). 129 12. Evans, J. c., and I.G. M~rgan: The Application- of Pneumatic.Gauging to Hig~.Precision Linear Measurements, J. Sci. Instruni., 33, 388, (1956) • . 13 •. ------' I. G. Mor~an, B. s. W. Mann, · and .F. C. P. Mason: Continuous Thickness Measuring pf Thin, Soft Sheet, Engineering, 184, 631., (1957). 14. Frolich, ·I:i.: Dielectric Breakdown in Ionic Crystals., Phys. Rev., ·56, 349, (1939). 15. Garton, C. G., and H. F. Church: Electric Breakdown of Organic Insulators by Electrochemical Reactions, Nature, 162, 301, (1948)·. 16. McLean, D. A., and L~ Egerton: Paper Capacitors Conta~g Chlorinated Impregna.Iits, Ind. Eng. Chem., 38·, 512, (1946). 17. Morgan, I. G., and D. C. Barnes: A Pneumatic Comparator for . . Me~suring Variations in .Bore Diameters., Engineer, 200, 7~5, (1955). · 18. Oakes, W. G.: · Intrinsic Electric Strength of Polythene, Nature, 159, 29, (1947)~ . 19. ------· The Intrinsic Electric Strength of.Polythene and its Va.riation with Temperature., J. Inst. ·Elect. Engrs., 2§., part 1, 36, (1948). 20. ______: The Electric Strength of Some Synthetic Polymers, . . J. Inst. Elect. Engrs., 96; part 1, 37, (1949) • . 21. Schwaiger, A.: "Theory of Diel.ectrics", p. 35. John .\viley & Sons·,-· ·Inc., New York, 1932 • .22. ib~d, p. 36. 23. ibid, P• 38. 24. Shortley, G., and D. Williams:· "Elements of Physics", p. 596. Prentice-Hall, Inc., New York, 1955. 2 ed. 130 25. Sutherland, R. O.: "Laboratory Notes for Physical Chemistry"~ p. 17. Bardgett Printing & Publishing Co., ·st. Louis, 1957. 26. Thomas, A. M., and W~ L. Gent: Permeation arid Sorption of Water Vapor in Varnish Films, Proc. Phys. Soc~~ 57, . 324, (1945}. 27. ------' and M. V. Griffith:" Intrinsic Electric Strength and Condu~tivity of Varnish Films and Their.·variation with Temperature, . . J. Inst. Ele~t. Engrs., 89, part 1, 487~ (1942). 28. vo·n Hippel, A.: Electric Breakdown of Solid and Liquid Insulators, . J. App. Phys.,~' 815, (1937). 29. ------' and R~ s. Alger: Breakdown of Ionic Crystals by Electron Avalanches, Phys. Review, 1§., 127, (1949). 30~ ------' and G. M. Lee: Scattering, Trapping, and Release of Electrons in NaCl and in Mixed.Crystals of NaCl and Agel, Phys. Review, ~~ 824, (1941). · 31. Whitehead, s.: "Dielectric Breakdown of Solids"·, pp. 23 - 39. Oxford Press, London, 1951. 32. ibid, P• 56. 33. ibid, p. 115. 34~ ibid, P• 242. 131 IX. ACKNOWLEGMENTS The author wishes to express his sincere _appr_eciation to · Dr. Wouter Bosch for his advice and d.irec~ion Qf this research. · With out his encouragement and assistan.ce during . the past. two years, . the goal of this investigation may not have been reached. He wishes to thank·Dr. H. L. Bowkl.ey for suggesting this invest igation. The author wishes to thank Dr. Wm. J. James for his help an~ guidance on the use of statistics in this problem. To Mr. o. K. Lay for his help and guidance on the construction of the thickness gage and to Mr. R. T. DeWoody for ·hisvaluable assist ance on the voltage determining circuit, goes special thanks. To the. au~hor's wife goes the ltarmest appreciation for her inspi ration and encouragement. Without her help·, and sacrifice, the completion of this thesis would not have.been possible. X. VITA John Harvey Gustafson, son of Harvey J. and Elsie S. Gustafson, was born at St. Paul, Minnesota, on August 20, ~936. Grade school education was obtained·at Chelsea Heights ~blic School (1941 - 1948), St. Paul, Minnesota. He attended Ramsey Jm1ior High School (1948 -1951) and Washburn High School in Minneapolis, Minnes~ta were he graduated in May 1954. September.1954, he enrolled at the North Dakota Agricultural . College, Fargo, North Dakota and received a Bachelor of Science Degree in Chemistry in.May, 1958. September 1958, the author entered the Graduate School of the Missouri School of Mines and Metallurgy. He was a graduate assistant for three semesters {September 1958 to February 1960). Upon completion of requirements for the M. -Sc. degree, the author will begin work as a chemist for the Hawthorn Finishing Company, New Haven, Missouri. The author was married to Barbara Ann Bakke, June 7, 1958. He has one yonnger brother, Thomas Allen, who is in seventh grade.